Walkthrough & Gameplay Hints

Basic mechanics, hints and solutions for the main progression path from start to credits. This guide provides a cursory walkthrough with a focus on harder levels and common roadblocks. It aims to nudge you into the right direction first, before spoiling the full solution. Can also serve as a reference for the speedrun achievement.

Gameplay Basics

If you are struggling with the really basic mechanics, this not really the guide for you, but I suggest you play the game's demo. It has its own set of levels and I would argue that the difficulty curve is gentler and the tutorialization better. If you've already bought the game on Steam there is unfortunately no easy way to play the demo on the same account. But the demo is available for play online (in your browser) on the game's official itch.io page[armor-games-studios.itch.io], so check it out if you want an arguably better introduction to the very basic concepts

Here, in this guide, I would rather cover some important mechanics that lack a proper explanation in-game or that at least could use a reference to look them up. If you think figuring out mechanics is part of the fun, you should skip this section. Personally I think a puzzle game should generally make you aware of all the options you have, so you can work out solutions without having to guess.

The Rules of Colour Mixing

The game follows additive colour mixing: Red and green make yellow, red and blue make magenta, green and blue make cyan, and all three basic colours together add up to white. Later on you will encounter mechanisms to break apart mixed colours into their constituent parts or filter out some of those parts.

Collision Patterns

When two photons collide they annihilate when the collision is head-on. Every other collison causes them to merge and to potentially change their direction. Not all direction changes are exactly intuitive, but it is important to know all available options.

Splitter Colour Patterns

There is a handy mnemonic to predict which side to expect a colour from when splitting composite colours: Starting from the input, the outputs will always follow the order "RGB" in clockwise direction (skipping colours that are not part of the input of course).
This is also the orientation of the big branches on the map: You come into the central hub from the prologue at the bottom with a white beam, then the red branch extends to the left, the green one to the top and the blue one to the right. This principle is very consistent through-out the game, which makes it all the more hilarious that the game's promotional artwork (most notably the huge banner on top of your library) shows you a wrong (mirrored) split. Don't let that distract you, just follow the "RGB" rule.

Collisions on Mirrors

There is a weird edge case when multiple photons meet on a tile with a mirror present. Collisions always take precedent over reflections. That means the collision happens as if the mirror didn't exist and only then the end-product of the collision encounters the mirror.
If two photons come at the mirror head-on from different sides you might expect them both to reflect, but head-on collisions always annihilate before anything gets to be reflected (first image). If you want to "double-use" a mirror you have to make sure the photons are on different cycles (second image).
Right-angled collisions produce a normal diagonal beam that is then reflected back on itself (third image). Acute-angled collisions are bent 90° since they would continue straight without the mirror (fourth image).
And if there is a filter beam on the same tile, even if it is only on the other side of the mirror, it will strip the colour components as if the photon had passed through it before the photon is reflected by the mirror as normal (last image).

Switch Mirrors

After every photon hitting a switch mirror the mirror pane changes its orientation by 90°. This has two main uses:
1) It can merge two inputs. In the left image cyan and magenta come in from the sides at a 2-beat offset and get merged into a single beam. Up to 4 full beams can share space as long as they are on different cycles. This even works for beams travelling in opposite directions although this is never part of a required solution. The main advantage so far is that you can get multiple beams through narrow gaps and that merged beams will use less mirrors to direct the same amount of photons. Sometimes you will also have to turn 2 "half-beams" that each consist of every other photon into 1 full beam.
2) It can split a single input evenly into two. In the right image the doubled up beam from the last example comes in and gets split back into its constituent magenta and cyan beams which then go off to the sides.
Quite often you will find both uses one after the other like in the example images. A common problem with switch mirror structures is that a short beam interruption can cause them to go off-cycle. In case of a merger the output might go into the other direction (up in the left image) and in case of a split it might reverse the colours. Usually the switch mirror can be manually toggled to bring everything in line again, but sometimes you have to find a way to manually discard a single photon to get it back in cycle.

The Generator

This is a very powerful formation that will crop up a few times during play (sometimes required, other times you can break intended solutions with it). We trap a photon in an endless loop, but one of the mirrors is a horizontal splitter, duplicating the photon every 4 beats. This allows us to essentially create our own emitters to set up a new beam of light anywhere we want. In theory this can be extended into a double-generator by replacing the far mirror with another splitter, but I have not found a use for that so far.

General Hints

Some general pointers first:

1) Find stable solutions. At several points the game allows for unstable solutions where beams interfer with each other causing regular interruptions or where you have to manually help out. This is basically never the proper way forward and you should consider reworking your layout until you can deliver a stable, uninterrupted stream of the required output.

2) Transport components between screens when possible. Every screen has a 1-tile border shared with all adjacent levels. If there is a gap in the wall that allows placing components it is almost always a hint that you are supposed to ferry equipment back and forth.

3) Consider working backwards. Often (but not always) the biggest restrictions will be towards the end (a single lane to access the repeater you're trying to unlock, a single diagonal passing through an otherwise solid wall, etc).

4) Look for isolations. This will become more important later in the game (especially in the green branch), but sometimes areas in the same screen are isolated from each other (by a combination of walls, glitches, impassable diagonals, striped tiles, etc). When you enter a new screen do a quick pass to spot these separation lines. Sometimes you can immediately turn around because your entry point is useless.

5) Don't be shy to rework solutions after they've done their job. Repeaters stay unlocked and you can still use them to visit those screens if you redirect beams away from them. This goes especially in conjunction with the aforementioned isolations. Sometimes you have to do an elaborate set-up to unlock a new screen, just to double back and rework everything because the repeater is isolated on the other side.

6) Use striped tiles (the ones that don't allow placement of objects on them) as a guide. Very often single tiles or lines of them denote important places in the screen, like the locations where two beams are supposed to collide.

7) Click on components and hold the mouse button to temporarily disable them. This is very useful to synchronize complex layouts, especially to shift a head-on collision to a different place.

Map and Introduction

The following walkthrough will not hold your hand through every screen; look for a video guide for that. I will gloss over most easy or straight-forward solutions and focus on the screens with some difficulty or conceptual challenge. This guide is intendend more as a resource where you can look for help with specific challenges than a complete step-by-step narrative. As such a full map for orientation is more important than keeping you completely spoiler free:
The X marks the game's central hub (with the battery display in the middle). There are four major branches: Prologue (P), Blue (B), Red (R) and Green (G). Each branch has a first half (a) and a second half (b), each comprised of several screens (numbered on the map) and culminating with the unlocking of a number tile (which triggers a small in-game cutscene).
If you only need help with a specific level you can search (CTRL+F) this guide for its code (like Pa03 for example) and it should take you roughly to the right part of the guide.

Prologue A (Number 2)

The Tutorial (Pa01-Pa11)

Not much to say as you shouln't be facing a lot of resistance. To enjoy the benefit of the tutorial try to make mental notes what each screen is trying to teach you (every screen basically shows you some new interaction).
Encountering the glitch for the first time in Pa05 will give you an achievement.
In Pa06 you need to ignore all pre-built mirrors but the first.
By Pa08 you might have noticed that it is generally a good idea to understand the striped tiles (on which you can't build) as an indicator where beams can or should go. This holds true for most of the game.
In Pa09 don't overlook the blocker in the bottom on the green path.
Pa10 is a bit evil in that it immediately subverts the "rule" learned in Pa08 because this is one of the very very rare levels where you have to ignore the path laid out by the striped tiles. The solution looks like this:

The first Number (Pa12-Pa13)

In Pa12 we make a small detour to the left (Pa13) where we take the first gap upwards. Back in Pa12 feeding 4 photons to the number will activate it and give you another achievement.
Now that all the glitches are gone we can continue down below to the other half of Pa11 and into the next area.

Prologue B (Number 1)

Diagonals (Pb01-Pb03)

In Pb01 we learn about colour merging, collisions and diagonals. The left-most striped tile is once again helpful and marks the perfect collision point. Do note how the locked repeater (the goal) accepts inputs on a diagonal.
Pb02 hits home the importance of timing. You should only focus on the red beam and leave the main yellow beam alone. Specifically pull the red beam 1 tile down to avoid the collision point on the striped tile, then pass through yellow and upwards to collide on the other striped tile.
In Pb03 we can only feed one of the three repeaters and since it's tucked away in a corner we have to hit it at a diagonal coming from below. Redirect the top beam until it hits our main beam from the right.

Wrangling Beams (Pb04-Pb07)

First we learn about imprintable repeaters at the top of the screen - they have an empty box and accept any input. Then we need to find the right timing and collision points: Red is bent upwards at the right edge of the screen so it hits yellow on its first tile and bends it diagonally upwards towards the left repeater. Green is bent upwards 1 tile from the edge to go straight into the right repeater. On top in Pb05 green makes a bend to hit yellow diagonally downwards following the striped path. Adjust green's timing as needed by making the bend 1 tile higher or lower which offets the beam by 2 beats.

In Pb06 there is no blue in sight, so we have to bend the yellow beam downwards somehow. Since it only goes along striped tiles we have to rely on collisions to redirect it. Just the way the level is set up, the game forces you into a slightly convoluted solution. If you think you're lacking some parts check out the screen above (Pb07). You are supposed to turn both beams around up there.. If your timing doesn't match up adjust it in Pb07 just like you did in Pb05. Full solution:

Reworking Solutions (Pb08-Pb13)

We are now in Pb08. In order to advance on the next screen below (Pb10) we need a green beam which we can get from the screen above (Pb09). To unlock Pb09 one way is to put a downward mirror in front of yellow's entry point and hug the wall clock-wise until you end up in the top-left repeater using only pre-built mirrors. Up there we need to bring the green beam in line with the repeater using 2 mirrors and then prevent a collision by bending the middle cyan beam away. Now we need to rework Pb08 to guide both yellow and green down. If you are lost amidst all the pre-built mirrors you can almost entirely stay on the right half of the screen for your solution. But it is important to remember that you can "double-use" a mirror if the beams are on different cycles. Solution: Put a mirror right in front of the yellow input repeater and reflect yellow down. Then use that mirror and the pre-built mirrors to get green to where it needs to be. Finally use the last movable mirror to put yellow into the goal.
Pb10 should now be self-explanatoy making the same "double-use" of the pre-built mirror after swapping all the blockers to the middle.
Onwards to more rework shenanigans where in Pb11 you first unlock the screen above (Pb12) and then use the blue beam from there to guide the yellow beam into the goal in Pb11. Shouldn't be very difficult since the path is once again marked by striped tiles - just bend the yellow 1 tile upwards then down again right after after passing the middle wall.

Pb13 is just a short introduction to filter beams. Simply take the left path.

Multi-Screen Puzzle (Pb14-Pb17)

In Pb14 the left repeater should unlock automatically, then unlock the the upwards repeater by parking the mirrors in the cubby in the top wall - note that this cubby is shared between this screen and the one above. Up there in Pb15 you should first note that your yellow main beam dead-ends, so we can safely remove later. Bend the green up through the right gap, pass the blue beam and go immediately back down so the green perfectly hits the blue onto the diagonal towards the repeater. In Pb16 line up the cyan with the pre-built mirror. Backtrack and go into Pb17 where you remove all obstacles and place the single mirror. Finally we can move on and automatically pass through the top-half of Pb12.

Redirection Challenge (Pb18)

This is the first moderately challenging level that acts almost like an exam of everything you've learned so far. Unfortunately it's mostly execution, so there are not a lot of hints I can give. If you haven't already you might want to check out the collision patterns in the first chapter to make sure you're aware of all of your options to redirect the main beam. You might also want to note that the level isn't entirely symmetrical and this really matters for the solution. Picture of the final product:

The Great Back-and-Forth (Pb19-Pb25)

Finally we see the next number tile in Pb19. So close and yet so far! Check left if you want, but there is nothing we can do over there. To the right we go! You now enter a sequence of screens that is split in half. Focus on the bottom half and on unlocking new screens. Don't worry about the other half for now. Use whatever mirrors you have available. In Pb22 you should end with a mirror left over. If you get stuck in Pb23 note the gap in the wall - you are supposed to bring the left-over mirror from Pb22 with you. Finally in Pb24 our white beam meets a dead-end. Liberate the red beam by going through the center and then around below the glitch and bring it upwards through a gap in the wall. Now we start the long hike back where along the way we will completely cannibalize our original solutions. We don't need the original beam anymore, so now we play entirely in the other halves of the screen. In Pb23 merge blue and green into your red beam for white. Once again notice that the striped tiles show you exactly both collision points and the short diagonal path inbetween. In Pb22 we find ourselves short one mirror, but thankfully there should be one left over in Pb23 that we can bring back with us.
Eventually back in Pb19 you need to navigate the glitch maze with the beam coming from the upper right until it exits at the bottom left. Also redirect the original beam coming from the bottom towards the middle right. Over in the next screen (Pb25) make them collide and hit the left repeater. Finally we hit the number tile in Pb19 and get a well-deserved achievement.

Learning about Switch-Mirrors (Pb26-Pb27)

After redirecting the original beam through the now clear path upwards we reach two short tutorial rooms about switch mirrors, each asking you to build one half of a common pattern. More than anything it's trying to teach you that switch mirrors are sometimes off-cycle and need to be brought in line. In Pb26 you can do that by manually toggling the switch mirror. In Pb27 you might need to discard a single photon from a side.

Finally we finish the Prologue and reach the game's central hub. There is of course an achievement, but the true reward is one of the best music loops in the game! Simply restore the solution that you saw during the cutscene.

Blue A (Number 3)

You now have the choice which side to continue at. We'll go right for now.

Introduction to Splitters (Ba01-Ba03)

Just a couple short tutorial levels at the start of the branch. In Ba01 you split and then collide to follow the marked diagonals. In Ba02 you learn that orthogonal splitters preserve directions while diagonal splitters change directions by 45°. Just hug the diamond in the middle with two diagonal splitters in line with entry and exit.
Ba03 is slightly more tricky. Two mirrors in the top row and then one long diagonal crossing through both X-ray beams will do the trick.

Triple Blue (Ba04-Ba09)

Now for a larger multi-screen puzzle.
In Ba04 you frist need to remove interference from the blue line. Simply place the splitter in front of the left X-ray emitter. On to Ba05. Just curve the beam using 3 splitters until it hits the top repeater. Upwards (Ba06) seems to be a dead end for now since it needs two more inputs. But we can progress in Ba04 by bringing the left-over splitter back from Ba05 via the gap in the wall. Then we put the second splitter in front of the second X-ray emitter and they'll now merge up and unlock the repeater at the top of the screen.
We arrive at a small new hub (Ba07). You can unlock the two repeaters seperately and explore around, but ultimately we are going to need both the yellow and blue output to receive a steady stream of photons. Finding a stable solution is kind of tricky and relies on careful positioning of the splitter (so the colours are coming out in helpful directions) and double-using a mirror since you don't have enough parts otherwise. Solution:

The way forward is to the right in Ba06, only we still need one more blue input.
Our last remaining option is following the yellow beam from upwards into Ba08, which can be another tricky roadblock. Conceptually it's no secret that we need to take the green component out of the yellow and merge it with the blue already present to form the target cyan. If you're stuck take a good look at all the collision patterns at the top of this guide and try to think a litte outside of the box with them. Hint 1: There are no diagonal beams in this level.. Hint 2: It is a matter of timing; half your infrastructure will be spent getting the timing right and only half to form cyan and direct it towards the target. Hint 3: Look at colliding green with both blue beams at the same time. Solution:

On to Ba09 for our first real application of switch mirrors we learned about at the tail end of the Prologue. More than half the level is already built, you just have to fill in the blanks. Start symmetrically to the magenta side then put your remaining splitter at the crossing point. The old timing issue can once again rear its ugly head, but you only need to pass 1 photon of any colour through the middle splitter by clicking on it for about a second to switch the output sides.
Finally we have all the inputs for Ba06 and can solve it by putting the splitter right in front of the left entry point and toggling it to diagonals.

Various Timing Issues (Ba10-Ba12)

Ba10 is just a fairly boring timing-based level. One of many solutions:

Ba11 teaches you that diagonal beams travel faster and the length of the diagonal can therefore change the timing. The solution requires just a 1-tile diagonal through the gap.
Ba12 puts splitter routing and timing together. You should probably keep it symmetrical. One of many possible solutions:

Splitter Routing (Ba13-Ba14)

Ba13 is pretty straight-forward. Ignore the markings. Simply put a diagonal splitter right at the start and take it from there. The rest is just hugging walls.
Ba14 is conceptually simple. There is only one way to have red and blue merge and end up on a straight beam towards the goal, and that is a red diagonal from the top-left and a blue diagonal from the bottom-left colliding in the middle. So how to do it? It's fairly obvious that we need a symmetrical solution. We somehow have to collide both red beams and both blue beams to send them each onto the diagonal we need.. The pre-built infrastructure gives a hint that we should probably take the long way around, hug the outside wall until we pass the emitter. All that is left is immediately turning around for the required collision.

Missing Colours (Ba15-Ba18)

In Ba15 we don't have any green, so there's only one way to go. The same is true in Ba16.
In Ba17 we finally find our missing green. Simply let the green diagonal collide in front of the green emitter and then direct the resulting beam into the goal. We can completely ignore the other side.
Back to Ba16 and things are starting to get complicated. To get the green outside of here we need to turn it into cyan. That requires blue, but we only have 1 blue component which is tied up in the magenta beam, which also happens to contain our only red. How are we supposed to create white in Ba15 if we take blue out of magenta and discard the red? Admittedly this is one of the mechanics with the weakest tutorialization. The key is the pre-built structure in the top-left. Leaving the splitter on diagonal as is, makes this a weird diagonal reflector/splitter that produces an interesting but unstable solution. Toggle the splitter to orthogonal and think about what this formation of mirrors can do for you. It is your first encounter with a generator! Send a single magenta photon in from below and the blue component will be forever trapped, creating a new beam towards the left. And that finishes the room since cyan is already on course for the repeater.
Finally back in Ba15 we just need to merge cyan and magenta. Direct cyan upwards at the left-most tile, then collide magenta so the result heads diagonally towards the goal. Easy. Ba18 unlocks the next number and achievement.

Blue B (Number 4)

Splitter Overload (Bb01-Bb04)

Bb01 is soft start before things start getting crazy. Remember to keep everything symmetrical. Another hint is to not feel like you have to use every component on offer - there are very simple solutions that only use half. Simply park the orthogonal splitters in the corners and use the diagonal splitters on the outsides.
Bb02 puts the splitter challenge into overdrive. For the one spliter you can rotate you want to keep it diagonal like everything else, although it should be noted that the rotating splitter is not first in line. Somewhat surprisingly the solution is still symmetrical, despite the level being not. Full solution:

The way forward goes up, but we need a lot more inputs there so let's follow red to the left into Bb03. The only way to get to the goal is putting an orthogonal splitter in the center and shooting a diagonal beam at it. But how do you make a diagonal beam with only one input? Think back to the previous section. Yes, the formation in the bottom center is a generator once you complete it with a splitter. Timing is of the essence, so to properly start the generator you'll want to reflect 1 photon from the original beam down onto the pre-built mirror and then over to the rotating pre-built mirror. Use that to feed the splitter from the left, then switch the mirror around to close the loop.
Bb04 is once again a splitter maze. Try to work backwards until you have a solution that uses every single splitter. In a picture:

That's our second input into Bb07 but we need one more. Back in Bb02 let's now follow the blue to the right into Bb05.

Splitting just to Mix again (Bb05-Bb08)

In Bb05 remove the central splitter and use the by-now-familiar switch mirror pattern to get both white beams upwards through the gap onto the pre-built switch mirror. Now that we have two white beams again we just have to split them and collide their red and blue components. The splitters are the next component after the switch mirrors and the rest should fall into place from that.
Bb06 is a pretty clever level that pushes switch mirrors to the next level. After a forced halving of your beam you have to find a way to make it whole again. This is in a way a counting exercise since both beam halves must stay on the same 4-beat-cycle. But take note that you don't have to merge the photons back up in squence, so one path can take a much longer way than the other, as long as it is only longer by multiples of 4. Full solution:

And finally we get to assemble everything together again in Bb08, which is a fairly tedious exercise in avoiding unwanted collisions and still synchronizing everything. Note that you can cross beams as long as it's before you synchronize them. Also some pre-built mirrors will have to be ignored. Just the way delays can be implemented there are only a few locations that allow you to take a path that is longer by 2 so those must be where the synchronizing happens. Full solution:

Bb08 is a difficult level to give hints for as I suspect there are multiple solutions. Once again it's all about synchronizing your beams. Don't forget that you can cross beams and that diagonal beams are "faster" than orthogonal beams. Using diagonal beams to merge up put me in the awkward position of needing a offset of 3 which you can only get with a weird non-symmetrical solution like this:

The Big Room (Bb09-Bb12)

Now for a big interconnected challenge. In general note the various gaps in the wall - there's going to be a lot of ferrying of equipment.
Yellow is the only way forward in Bb09, which shouldn't be difficult. In Bb10 we need cyan and might be tempted to rework our solution, but this is a trap. Keep yellow intact for now.. Start by sending two mirrors back to Bb09 to bring blue through the gap above the repeater. Then the remaining 3 mirrors to send blue down in Pb10 go upwards in line with the goal, which should collide your blue with the diagonal green directly after the splitter.
Beating Bb10 unfortunately leads into a dead end in Bb11. Time to rework everything! In Bb09 we set up a cyan diagonal using two mirrors and the markings on the floor for the collision point. Now pool all 5 remaining mirrors in Bb11. We would like to go left, but we can't yet, so let's ignore the left edge of Bb11 for the time being and focus on reassembling cyan to go right. Using 4 mirrors (1 on blue and 3 on green) you can collide the beams to diagonally hit the repeater. Bb12 is the big conceptual challenge of this area. Since the repeater in the bottom is fairly pointless, the only real goal of Bb12 is to assemble a beam that we can send back to the left to solve the left edge of Bb11. There are several unstable or manual solutions that would allow us to unlock the next screen, but ultimately we will need a stable stream of cyan going left. Considering how there is a switch mirror at the start and at the end of the horizontal line we will have to take - how can we ensure an unbroken stream of cyan that goes through two switch mirrors which each try to halve our beam? The conceptual solution is to use the first switch mirror to double up the beam by merging in the X-ray on an offset cycle. As an implementation pointer, we need to bring our last remaining mirror from Bb11 with us to feed cyan into the merged beam from above and the X-rays from below. Full solution of Bb11 and Bb12 in picture form:

The Final Corridor (Bb13-Bb15)

In Bb13 we have no way of influencing the cyan beam and two mirrors aren't enough to directly bend away the three vertical beams, so we'll have to find a way to set up a chain reaction. The solution is to put one mirror above the discarded X-ray in Bb11 so it gets directed into Bb13, where it collides with the first beam and then the second. Then use the final mirror to bend the third beam into a wall.
Bb14 is again just fiddling with splitters until we find a solution that fits. Conceptually we can once again make use of the striped tiles as indicators for our (downwards) diagonal. For the bottom two splitters are enough, meaning you'll have to find a way to get the green beam to its target with 4 splitters. Solution:

And that's it for the blue branch as Bb15 contains the number 4 and also lights up the blue antenna for 2 achievements.

Red A-1

With the blue branch done we go back to the central hub and continue left into the red branch.

Filters Tutorial (Ra01-Ra05)

We have briefly encountered them before but now we will really get into filter beams. Ra01 is a reminder of the basic concept (they filter all colours that are a component of their own colour).
Ra02 forces you to acknowledge that you can bend filter beams using mirrors.
Ra03 is more about removing mirrors than placing them. The blue filter doesn't bother anyone, the red filter should not be reflected at all and the green filter needs to be pulled out to filter the white light after the three photon beams collide in the middle.
Ra04 teaches you that filter beams can be blocked - both by blockers and by other filter beams. Start by snaking the cyan filter beam (the only one that doesn't interfer with red light) around and using the blocker to reset the magenta and yellow filter beams so the cyan one ends up blocking them. Then use the blocker on the final red filter beam.
Ra05 is fairly simple. Strategically place blockers and use the pre-built mirrors. Very easy if you work backwards from the goal and realize the glitched tile leaves only one viable way.

Selective Filtering (Ra06-Ra07)

On Ra06 conceptually your options are limited: the bottom is blocked by the red filter and for snaking red through via diagonals you have too few beams - so ultimately it's going to be a straight line through the top. Use blue for the first collision putting red (now magenta) on an upwards diagonal, the use green to level it out. The gist of the solution:

Ra07 is a bit of high-concept fun with filters. Note how you can't redirect the photon beams in any way, so all you can do wrangle the filter beams until three pure red beams collide and move into the goal. Just think about which filter beams you need to pull the unwanted blue and green components out of the photon beams. Note that this level makes use of the fairly quirky edge-case rule that a photon beam and a filter beam hitting the same mirror from opposite sides still interact (collisions apply before mirrors). Solution:

Intro to Switches (Ra08-Ra12)

The glitch monster is being a jerk again and toggles mysterious new switches to block our way. Go to the right by double-using the pre-built mirror; adust timings as needed.
In Ra09 we learn about switches hands-on. Note that switches always have these four diagonal lines that distinguishe them from inactive switchblocks. Also note how useful sending single photons is to avoid re-toggling the same switch. Taking the upper exit we go back to Ra08 to hit another switch by borrowing a mirror from below. This opens up a new way to the left.
Tons of equipment but not much to do in Ra10. Neither do we have white light, nor anything to set up a diagonal. Down we go. While we're at it we take all three remaining mirrors with us using the three gaps in the wall.
Ra11 is the switch-and-filter exercise, testing what you've learned in the red branch so far. This level partly relies on filter beams blocking each other, which means priority matters and merely toggling a switch will not always restore the previous state of the level. The first steps are fairly linear: The right switch is enclosed by filter beams, while you can reach the left switch by bending the top filter beam. This will give you access to the other side. Note what each switch does: The left switch only enables and disables the vertical filter beam in the middle. while the rigth switch toggles all the other switch blocks - the goal blocker and both horizontal filter beams. Conceptually we need the vertical beam off (left switch) to reach the right switch. Since that switch controls access to the goal, its final position is a given, but that would unleash the bottom filter beam. Ultimately it's unfortunately a level relying on timing. Toggle left switch to turn off the vertical filter beam. Send a single photon down to the very bottom and to the right, reusing the same mirror. Once that photon has crossed the center line you need to send a photon into the left switch to turn the vertical filter beam on again so it blocks the bottom filter beam once the right switch is toggled. Take note that you'll want a mirror in the top center gap to avoid having the vertical filter beam cut your beam in Ra10.
Ra12 tantalizes us with the number tile but sadly does not allow any player interaction.

Interlude (Ra13-Ra14)

In Ra13 we need to collide beams to reach the exit, but the filter beams block us. Start by using the right beam to toggle the switch in the bottom right using one of the pre-built mirrors. Then take the blocker from the center and use it to stop the filter beam coming from the left. Lastly we need to collide both red beams on the left to create a diagonal through the center. Let the main beam bounce off of two pre-built mirrors, then immediately turn it upwards. Use the second mirror to bend the bottom beam to the right for a collision.
Ra14 is all about figuring out timings that work. We need pass through the filters and collide all three beams. It's pretty fiddly and beams will criss-cross everywhere. I suspect there are multiple solutions but I settled on creating cyan first. My solution:

Red A-2 (Number 5)

Four-Screen Challenge (Ra15-Ra18)

This is perhaps my favourite area in the whole game. It's just a really neat conceptual challenge of four interconnected screens that seems convoluted at first but has a really logical and elegant solution. Once you have unlocked all four screens and played with all the switches give it a good thinking. We have two white inputs and in the end we need to feed yellow into a repeater. You also have three environmental filter beams (yellow, magenta, cyan). What options do you have to crate yellow? Since all filter beams have 2 components to them, you will always get a only a single basic colour out of filtering white light. So there is no direct way of getting yellow. Instead we will have to filter our two white beams into red and green and then assemble yellow from there. By this time it should come as no surprise that this will happen in Ra17 on the diagonal in front of the yellow repeater marked by striped tiles. So now that the goal is clear, we have to think about how to achieve it. The first obvious note is that nothing is ever allowed to pass through a yellow filter beam since it would remove the components we need. That leaves only one job for the white beam emitted in Ra16 - to immediately pass through a magenta filter beam and turn into green. Which tells us the other white beam with which we have entered this whole area must somehow turn into red for which we again have only one option (passing through the cyan filter beam in Ra17 from right to left). That clears up the concept, now all that is left is routing. Note that all screens share an open tile in the center allowing you to freely transfer equipment between all of them. As a hint you will use all of your equipment but one and also all of the available repeaters but one. If you are having trouble creating green light you need to release the magenta filter beam in Ra16 first. Toggle the switch in Ra16 if you haven't. Then go left, back to Ra15 and make sure the yellow filter beams extend vertically (toggle the switch if you have to). Going back to Ra16 will cause the magenta filter beam to update and extend. Now you can reset the switch in Ra15 and the horizontal yellow filter beam won't extend since it's blocked by the magenta beam. If you find yourself short 2 mirrors in the end, go back to Ra18 and think about how you could simplify it some more by crossing beams. Full solution for the whole area:

Filters and Switches (Ra19-Ra23)

Ra19 puts us back into the filter beam and switch master-class. I struggled quite a bit with this level. It is hard to give hints. If you've tried to make sense of the level you've likely toggled the switches a bunch and everyone's levels will look quite different as a result. For reference though from the initial state when you first get to the level, every switch needs to be toggled once - but beware, the switch with vertical lines needs to be toggled before the one with horizontal lines. As a general hint the blue beam will be left undisturbed. You will make use of every beam of light exceptthe red beam emitted in the bottom. Green goes right and is the first collision with the main beam coming from the right. Then two red beams coming from the top will be used to redirect the yellow beam towards a collision with blue. Final state of the solution:

Ra20 is just a short showcase of another implementation of the "collisions happen before mirror reflections. Let red and blue collide on top of a mirror to create a magenta beam diagonally between them. Picture:

Hope you like switches, because Ra21 has you covered. Toggling the far left switch once and then never again is a no-brainer (it opens the entrance). And surprisingly that's already enough to unlock the repeater - simply snake down in an S-shape starting at the left-most tile the beam reaches and ending on the pre-built toggle mirror. If you've swiched a bunch and are unsure about your state the first two symbols in the top left of the main field both have to be off to reach the repeater with the aforementioned S-shape. Ah, but not so fast, the next screen immediately dead-ends in a glitch, so back to the drawing board. You need only 1 toggle to rework your solution and that is the right switch. If you are unsure again the first two symbols in the top left of the main field have to be off and on. Then go up as soon as you can, left as soon as you can and hug the wall downwards until you are in front of the repeater to go back to the pre-built mirrors.
Ra22 thankfully is a bit simpler again. Can't do much with the newly acquired white except bend it upwards. Then yellow has to go on a journey using all the available mirrors - down to reflect off of the pre-built mirror in the corner, then up until it's 1 tile above the collision point for timing reasons and 1 tile back down to hit the required diagonal.
For Ra23 toggle the switch and build a symmetrical sollution. Beware, our beloved striped tiles cannot guide us to victory directly, but we can still replicate their shape 1 tile above.
And now we've looped all the way around, back to Ra12 where we can finally unlock the number tile for another achievement.

Red B (Number 6)

Gaining Entry (Ra11, Ra10, Ra08 again; Rb01)

Unlocking the number tile in Ra12 removes the glitches in that room, which promptly interrupts our red beam and breaks a bunch of solutions. Bummer! But at least we officially won't have to care about keeping everything intact anymore. We are not quite done with the first half of the red branch (Red A) as we still have some unlocking to do. Follow the cyan beam upwards through Ra11. Back at the top in Ra10 we somehow have to collide our initial red with our new cyan onto a diagonal which hits the repeater. Time to cannibalize Ra11 for parts! You will need all 5 mirrors and no interference from the vertical red filter beam which means you have to toggle the left switch in Ra11 once to disable it. Arrange everything like this:

After toggling the switch in Ra08 we are finally on to a new area!
In Rb01 the only available path is upwards since we see no switch for the H-shaped switch blocks. Simply avoid collisions by going down to the open area and doing a small detour outwards to the left.
What follows is an intricate 3x3 multi-screen challenge. The second half of the red branch is short, but intense. Try to figure it out on your own, it's pretty interesting how things are interconnected and the guide spoils it heavily.

Up the Left Side (Rb02-Rb06)

Rb02 is our new hub and assembling white light to go upwards is the goal of the whole area. Apart from that we can go left, but our mirrors do not allow us to bend the red beam that way. So we will have to redirect the X-ray beam. Once the repeater is unlocked you can immediately remove the mirrors - otherwise the X-ray beam has a good chance of getting in the way later.
In Rb03 our mirrors again limit our options. Continue upwards with cyan for now.
In Rb04 note that cyan is practically at a dead end given our mirrors. Use magenta to go up once again.
In Rb05 ignore the main area for now and redirect magenta to the right.
Rb06 plays itself and now we've switched to the other side of the area.

Down the Right Side (Rb07-Rb09)

Rb07's striped tiles prevent coming at the goal repeater in a straight line (let alone we don't have enough mirrors), so clearly we need to come at it diagonally. Use one mirror to direct blue down so it collides with the magenta beam on the first striped tile in front of the magenta beam. And then use the other mirror to bend the red filter beam back so we get pure blue into the repeater.
Now we encounter a bit of a trap. Rb08 can easily be solved, but this will paint us into a corner down the line. Instead stay in Rb07 and rework the solution so it does not depend on magenta anymore. A single mirror can reflect blue down through the gap beside the repeater when you use one of your blockers to stop magenta from interfering. Take the remaining mirror and blocker down with you by placing them in the two gaps in the wall.

Rb08 is fairly simple especially with the two tools you bring in from Rb07 - you will even have some left over at the end. Use blockers and mirrors to impede the filter beams (a single mirror can block both white beams (remember that filter beams block each other), then place 2 mirrors to bring blue in line. If you want to future-proof things you should make sure the white filter beams are blocked from going left through the gaps in the wall as well - otherwise we will have to return later.
Rb09 is a bit more challenging. We need to find one solution that hits the switch and then another that brings blue to the goal.
For the first half use only X-rays and disregard the blue beam. Specifically bend the X-ray coming from the top left down directly after the two striped tiles, then level it out at the very bottom so it collides on the first tile of the other X-ray beam, sending a diagonal towards the switch. Take care to only send a single photon.
For the second half of Rb09 we simply have to remove X-ray interference as blue would go into the repeater on its own. Specifically you'll want to bend the top-left X-ray down after two striped and two empty tiles (one more tile right than the first solution) coming down to the close left of the four columns in the middle. Then level it out to collide it horizontally into the X-ray from the bottom at that beam's third tile so the new diagonal X-ray passes through the pane of the pre-built mirror.
That's the right side and the blue component done.

Down the Left Side (Rb05-Rb03)

Back to the top left corner of the area (Rb05). We have to bring green light from here all the way down. Remember that we reworked the top right corner (Rb07) so magenta wouldn't be needed anymore, so we can pull all mirrors out of the corner to use them on the main area. Conceptually since we want green we don't mind the magenta filter-beam, but the two others have to go, so simply bend the cyan beam upwards and reset the yellow beam for a moment so it gets blocked by cyan. Now for routing you should realize your limited options one screen down (Rb04) which dictate that we can't use the gap in the wall and have to go through the repeater instead. The solution entails putting down one mirror on the intersection of yellow and green (a "double-use" since they are off-sync) and the other at the very bottom of where green now goes (it will then merge with magenta and head for the goal through the filter beam).
In Rb04 we should once again remember that magenta isn't used anymore and that we can use all the mirrors. Remove interference by blocking green and white. Once again we can future-proof by stopping the white filter beams from going through the gaps in the right wall since we're already here - simply use a mirror to bend a white filter beam so it blocks the respective other on both sides, then use the blocker on green.
Finally back at the bottom in Rb03 we realize we have to shoot a diagonal beam into the repeater, which requires toggling the switch once. Use the bottom beam to toggle the switch, then collide both greens one tile to the right of the now disabled switch blocker in the bottom. If you are struggling with interference there is a way to set up a working solution while keeping the X-ray beam around, but you should really just go one screen right and disable it.

Finishing Off Red (Rb02, Rb10, Rb06)

Back in Rb02 all the colours will collide to finally form white and up we go to Rb10, unlocking the number 6 and another achievement. If you find yourself blocked by white filter beams you have to visit each side area and make sure both beams get blocked (remember that filter beams block each other, so a single mirror per side should suffice to block both beams).
This is all we need to unlock the green branch, but since we're already here - why not guide white beam upwards and through Rb06 into the red antenna to completely finish off the red-branch? Note that this requires you to cycle the switch mirror in Rb06 once by shooting a single photon at it from below, then just take the right path around the middle.

Green A-1

Back to the hub and up we go.

Entrance to Green (Ga01-Ga02)

Ga01 plays itself. If you want to learn about the weird symbols in this room, check out my Secrets Guide.
For Ga02 we need to get through and also filter out red and blue. Simply plug the white filter beams coming out the sides with blockers, then put the two splitters in front of the white filter beams in the middle.

Green to the Left (Ga03-Ga05)

Not only does the glitch take away the hint system (what a jerk!), you are also entering the most demanding area so far. Everything up until now has just been a tutorial for the green branch. Virtually everything is connected in weird ways, virtually every screen will have to be solved and then reworked. Now would be a good time to remember that you can jump between rooms using the map in the pause menu.

Ga03 is a maze requiring some careful analysis. With so few gaps we clearly have to use diagonals somehow. Don't forget the green filter beam in front of the goal - you can freely use green light to redirect the magenta beam since it will get filtered out anyway. Simply pull blue down and along the bottom to collide with red onto a diagonal to the top right through the gap, then rectify the beam using green and the pre-built mirror.
Up to Ga04 - and immediately back again because we're at a dead end. Start the rework of Ga03 by toggling the switch on the left side to open up another path upwards. Then essentially repeat the script from the first solution but with swapped sides by pulling red along the bottom and colliding it with blue for a magenta diagonal (towards the top left this time), then recify using green and its pre-built mirror again. Beware, you have to swap one /-mirror for a \-mirror from Ga04 by using the gap in the wall.
In Ga04 bring everything with you that's still unused and quickly unlock the repeater on the right edge of the screen - it's another dead-end but we'll need access later. Simply block the green filter beam, come at the repeater from below and bring in the magenta filter beam from above to hit the final mirror from the other side so only green goes to the repeater. The bigger challenge is unlocking the repeater on the left edge. Where the two splitters go should be fairly obvious (right before the goal so the diamond-shape is completed). Clearly we need to set up a collision with the green beam emitted in the bottom left - there is no other way to get to the goal given how many striped tiles are around, so we probably want to come at it from a diagonal. As a hint, the proper solution uses every single piece of equipment, pre-built or not. To start use two mirrors to hit the pre-built splitter on the right, then loop the right output over the top and collide it with the left output to create a diagonal down. The remaining mirror keeps the green beam out of the way.

Many ways to do Ga05, but for a future-proof solution use the splitter on the first possible tile in front of the green filter beam going directly down, then reset the other (split) filter beam so it is now blocked too. Work backwards from the goal and realize you can't really reflect the beam upwards too often, so use 7 of your 9 mirrors to route the green down to the very bottom and around.

Magenta to the Rescue (Ga06-Ga07)

Up to Ga06 we go - and we're cut off from further progress. Checking out Ga07 we are lacking blue and can't really progress there either. Take a good look around and think about it until you notice the pre-built mirrors at the top of Ga07 and Ga05 - clearly we're supposed to send blue from left to right here.
In Ga06 our task is now finding a way to send blue down through the gap. Start by using 1 mirror to collide with green diagonally through the gap. Now all that's left is using 4 mirrors to send red straight down with the right timing (do a little detour to delay by 2 beats) so it collides with cyan and merges into white.
Back down in Ga05 we turn white around using the 2 remaining mirrors to hit the pre-built mirror in the top row sending the (now) magenta beam to the right (check the main solution above if you're having too few mirrors).

Now for Ga07 we finally have a blue component and can start by colliding the two green beams at the bottom to send them diagonally through the only gap. Immediately at the end of the diagonal gap we need to come in with blue from the right. Final product looks like this (2 mirrors not pictured):

Cyan Journey (Ga08-Ga12)

In Ga08 unlock the top repeater by any means necessary. A quick and dirty solution: right, split up, pre-built, up, left, split up. Once again we seem to be blocked everyhwere. Have you found the theme already? Yes, now cyan goes back left to the top-half of Ga06. This requires a pretty intricate solution. Conceptually the way the gaps and striped tiles are set up, we need to make several direction changes using green beams for collisions. As a hint you will once again have to use every single piece of infrastructure, pre-built or mobile. Full solution:

Ga06 is now a trivial redirection using the remaining mirror.

Ga10 is once again split in half (you know what's going to happen). Unlock the left.
Ga11 seems pretty nonsensical now, but since we're here we should send a blue filter beam to the right on the lowest row above the glitches. How to do this is hard to explain, so here's a short animation:

After what is pictured you just use one of the last two splitters to send the blue filter beam to the right. The last splitter is reserved for the green photon beam - more on that later.

Back to Ga10 to send the cyan beam to the right on the bottom-most accessible row (using 3 mirrors).
Finally let's progress in Ga09 on the other side. S-curve cyan around and unlock the repeater on the right. There's a diagonal gap with striped tiles ahead, so clearly we need some support from the right.
Head right to Ga12. Oops, all splitters! This is all about execution so I can't really give hints. Here's one possible solution:

Now we're ready to solve Ga09. The solution should now be pretty straight-forward. Send cyan up and use both blue beams to collide with it, then curve around all the obstacles from the bottom. If you have no idea how to get green out of your cyan, check above what you have to do in Ga11 to get a blue filter beam all the way over here.

Green A-2 (Number 7)

Green Overload (Ga13-Ga17)

Still at the end of Ga09 you can unlock the screen above now. Check it out if you want to, but going there at this time is a trap that just wastes our time until we tie up another loose end. Remember the unsolved top half of Ga10 and send the green beam from Ga09 over there on the top-most accessible row. Clearly we need a diagonal to solve the top half of Ga10, so it's time to bring in the green beam from Ga11 using the last remaining splitter on the second possible tile from the top. We are now able to unlock the repeater at the top of Ga10 by colliding like this:

Up we go for yet another screen split into two halves and yet another dead end. Down in Ga10 immediately rework your solution: The beam from the left needs to come in 1 tile higher (adjust in Ga11). Then use a single mirror to send it straight up through the gap Back up we go for another attempt.

For now Ga13 is used only to send green towards the right using a single mirror on the green beam. Unfortunately once we remove the white filter beam there is a whole lot of red light we need to stop from interfering, which we do by splitting the left white filter beam and curving it's red filter component around the whole bottom half. You should use all mirrors and reserve all splitters but one for the top half. The solution:

Remember how we reworked Ga10? Now the green beam coming in from Ga09 is no longer needed and we can rework our solution there. We really only need to relocate the last mirror and switch it around to send green towards the pre-built mirror and up through the repeater..

And now for a pretty dense level in Ga14. By now we should have two green inputs - one from the left and one from below. As a hint, the solution will make use of all available components, so think about how you can meaningfully incorporate the pre-built things. Given the presence of switch mirrors you should know what comes next: merge both green beams into a double-frequency green so you can pass both beams through the 1-tile-wide gap on the far right. In the upper half use the switch mirror to separate the beams again and send 1 full beam upwards and the other to the left. Picture of the final product:

Upwards the number tile is tantalizingly close, but we're not there yet.

Back to Ga13 for its upper half we go. Start with a diagonal splitter, followed by an orthogonal splitter. Ideally put the splitter you can rotate last, because naturally unlocking the repeater just gets us to a dead end. Simply rotate the last splitter and it should connect with the pre-built one, sending green up through the gap.
Ga15 is quickly solved using the two diagonal splitters for a curve.
Ga16 plays itself.
And finally, finally the first half of the green branch is over as we unlock the number 7 in Ga17 and get another achievement. Congratulations, this was quite the complicated area to keep track of!

Green B (Number 8)

Learning to Heal (Gb01-Gb04)

Gb01 is a throw-back to filter beams. Remember that filter beams block other filter beams. One possible solution:

Gb02 plays itself.
Gb03 introduces a new mechanic to heal glitched tiles.
Gb04 should be equally simple. Just collide green and blue onto a diagonal up to the left where the blue beam will turn cyan horizontal again.

First Position (Gb05-Gb07)

Not much we can do in Gb05 since we would need a diagonal to hit the healer and the way down dead-ends immediately (unlock it while we're here), so head left.
Still nothing helpful in Gb06, so continue left for now. If you struggle you have to rework the previous screen and come in through the gap, not the repeater. Use the second possible row from the bottom.

Finally in Gb07 we can set up a beam towards the right. Quickly unlock the repeater downwards for later convenience (for now there's nothing down there for us).
Ultimately due to all the striped tiles we'll need beams from the top and from below to meet in the middle. The simplest approach would be a fairly symmetrical set-up that collides two diagonal beams like this:

Back to Gb06 we go. Our goal is bringing the yellow beam back further. From looking at Gb05 ideally we would want to put the yellow in the top-most row so it hits the pre-built mirror in Gb05.
Finally with two beams in Gb05 it's payback time! Simply bring yellow into the pre-built mirror and level it out 1 row above cyan for a collision directly before the healer.

Second Position (Gb08-Gb13)

Now that the glitch has left a giant hole, we can continue downwards with our cyan beam. For that you have to bring in a single mirror from the screen below. In Gb08 and Gb09 we are constrained to a small corridor. Don't forget to bring the last mirror down with you. In Gb10 we meet our nemesis again and once again need more beams.

Continue left and down just to realize that our cyan beam is worthless here. Analyse Gb12 for a moment. How can the pre-built splitter be accessed and how do we get red light into the goal?
That means Gb11 needs a solution that sends red light down at a diagonal through the gap. That requires a red collision and we only have 1 red emitter and 1 pre-built splitter. This level requires a little thinking outside the box. Think back. There is an opportunity to set up our old favourite, the generator pattern, in the top-left using three mirrors and the pre-built splitter. End result:


Down in Gb12 we need to set up the second red beam. From the direction it needs to take (diagonally to the top right) we know we need a collision and it has to be between beams coming from left and bottom. That means we need to make some space on the packed loop below so red photons from the emitter on top can cross the loop and curve around to hit red photons on the loop from below. For that we will have to use the cyan filter beam (notice that switch mirrors are not triggered by filter beams, so use them here). Now all that's left should be a timing issue. Full solution:


Finally we arrive below our current target. Gb13 must be where we create the beam we need above. Analyse the screen above (Gb10). There are two ways to access the healer and only one works. Also notice the massive gap in the wall allowing you to exchange equipment. As a hint maybe there's a reason we have two red beams in Gb13. For a big conceptual spoiler: The approach to the healer will be horizontally from the right, which means you only need a single mirror in Gb10 and everything else can go down to Gb13 where you will need to set up a diagonal beam. Full solution to Gb13:

Take that you glitch jerk!

Third Position (Gb14-Gb15)

The glitch has now parked itself one screen to the right (Gb09) behind a wall. We would need to toggle the switches in Gb08 to be able to get our cyan beam in from the top. Let's work on that! Pushing the glitch out of Gb10 has once again opened a hole in the wall. Adjust your white beam 1 tile upwards and continue through Gb11 into Gb14. Send the red to the right. Then bring in green from above and also send it to the right. Don't worry about your solution in Gb07 (where have to go get the green beam) - yellow is no longer needed.
Now we have red and green in Gb15. Our end goal is sending a beam through the right-side gap. Two beams a pretty obviously not enough, so let's bring in more. Notice the gaps in the top? Let's bring in blue from Gb06! And we probably want two blue beams so we can collide two diagonals. Be aware that the blue beams should be offset by 2 beats because red and green below are 6 tiles apart. Thankfully we can completely cannibalize our solution in Gb07 so at least we have lots of parts. There are several possible solutions. Here is a really simple one but if you want to be fancy try and use a generator:


With four beams present Gb15 should now be no problem. Use the blockers to prevent interference as needed:

Then finally toggle both switches in Gb08: Bring in two mirrors from above (Gb05) and use the last one to send cyan down through the repeater. After the path is clear take all mirrors down with you and Gb09 should offer no resistance.

Final Position (Gb16)

Now for the grand finale. Check out Gb14. With the mirrors removed by the glitch - what options do we have? How about a three-way collision of green from above, red from below and blue from the left. That means we need to restore our setup for red and find a way to bring blue in from the right.
As usual our next step forward is where we just evicted the glitch from, in Gb09. What do we spy in the bottom right corner? A fresh new blue beam! Clearly that goes 1 screen up and then all the way to the left. If you are running into routing problems or a lack of mirrors you are way overthinking it - there is a really simple solution because the first tile of the magenta filter beam is not striped - place a mirror there to open up a path for the blue beam, then use a single mirror up in Gb08 to send it left down the middle.
That should leave us with 3 mirrors in Gb09 to restore the flow of cyan towards the left through the gap in the wall. That's red taken care of.

All that is left is removing all the interference in Gb14 and we are set. Follow the glitch to Gb16, toggle everything and we are done: Glitch taken care of, number 8 unlocked, green branch beaten and two more achievements in the bag. Well done, enjoy the credits!
Of course the game is far from over with several secret areas still waiting to be found, but that is a story for another guide.

Speedrun Achievement

The game also has a speedrun achievement. At a little more than 5 hours the timer is fairly generous, but you will likely have to replay the game on a new saveslot to hit the threshold. If you want to learn more about the clock and the number system it uses, head on over to my Secrets Guide.
The basic non-spoiler gist is that you need to finish the game before the in-game clock (situated in Ga01, one room above the central hub) hits the state depicted in the achievement's icon (see picture).

Some general pointers:
1) You only need to hit the credits in time by completing the green branch (getting all 8 numbers). Avoid all secret areas as they only cost you time.
2) Don't stress too much, you should have plenty of time. I completed my speedrun in barely under 2 hours and I definitely played suboptimally (writing this guide on the side).
3) The clock still advances while you are on the pause/map menu.
4) If you want to step away for a while either quit out to the main menu or make sure the game loses focus (by clicking out of the window or tabbing away). Due to a Unity engine default setting this pauses everything, including the clock.
5) Be aware that fast-forwarding also affects the clock, so don't use it carelessly. But if you just speed up wait times you don't lose any additional time from fast-forwarding (which is handy during a forced replay).

Good luck!

[Gatebase]

Keen eye! I see the links when editing and when I try to re-upload the same file I get an error message that it's already uploaded. Disappearing random images from guides is apparently something Steam just does. Learn something new every day. Should be all fixed now, thank you for reporting the problem.

[LupisLight]

Hi, thank you much for this guide! Just wanted to let you know there are a few images missing: The solution image for Bb11/Bb12 is missing as are the maps for the Blue A and Green A sections.

[Amicable Animal]

Hi there! I just wanted to pop in and say that this walkthrough is incredible. Thank you so much for taking the time to write it – I'm genuinely in awe at how much detail and care you've put into it, and I imagine it must be such a huge help for players. I'm only sorry I didn't see this earlier!

P.S. I'm always delighted to see when people find more 'efficient' solutions than the ones I designed, as it just goes to show how creative and clever the people playing SOLAS 128 are!