Updated 3rd times on Nov.10, after beating the game for another 5 hours further:

After 20+hrs of gameplay I still have to say this game require some aggressive balance work.
The visual is pretty good, new alien models look nice, but what most Sigma franchaise players expect is AS3 not this tower defence style thing.

Leaving that alone, about the game:

1. Troopers, their required stars to unlock/crystals to purchase, their combat capabilities, are unbalanced in general.
Some levels are proven impossible to go through linearly. You simply can't choose easy difficulty and beat all of them till the end. You HAVE to go back beat earlier levels on higher difficulty till you get all the money and stars to unlock better troopers. This makes it a total slog fest.
Flamethrower, Shootgunner and Rockeeter - without unlocking and upgrading them at least once, it is hardly possible to go further with low tier gunners. Unless you beat the starting levels repetitively to upgrade them in a crazy manner.
Flamer replaces Soldiers readily. Rocket renders Sniper useless - they are way more capable to repel hedgehogs and spouts than snipers. The secondary ability also clean the mess more efficiently. Defenders may prove less capable as a frontline tank than flamer early on, but their upgrades outpower flamethrower significantly later, plus far more useful secondary ability.
Elites are too expensive. It may be fair if the cost could lower to like 700-800, but 1000 renders it a pale choice as a ranged high DPS.
In late game you find soldier and sniper useless. No need to upgrade them anymore, just bank a ton of miners for opening, transition to defender.

2. Some level designs are questionable.
Although I played the game for 20 hours I still doubt this game have way too many suicidal enemy roles. It has never been so many in AS and ZS series and AH1. The kamikaze units make the gameplay quite tedious. Explosions are everywhere on your way, on every planet, on every single mission. I wouldn't say it is a totally bad idea but this looks stupid after you playing for hours long.
Acid pools last too long and force you to step over them, losing hp and repaired by medics - I doubt this mechanics and personally speaking this is stupid. You can avoid such scenario in AS/ZS, but this game it is unavoidable. Regardless how little damage it actually does, it is discouraging and an unclever design.

3. Slot design is insufficient, providing limited gameplay choices, making it very boring.
4 slot is not enough. It is enough to beat the game, but NOT enough to allow variable gameplay tactics. You have to pick a tank unit, a ranged unit, bring your miner and medic - ALWAYS. This means it has no variable choices in late game.
I would suggest 5 or 6, so you can transition from midgame to lategame for more diversities of tactics.

4. Medic may should be allowed to heal the whole squad instead of just whom around him. I am not sure if it will make it OP but otherwise you will always have to bring 4 medics to heal the whole phanlex, and thus your tactical choices are reduced.

Buy it if you a Sigma fan and want to have a glance at what will it be like in AS3. Or don't buy it if you can't tolerate all these above.

Another great time waster from this developer. Their games wont win a prize for originality, story or beauty, but if you are looking for a cheap game to blow off some steam (and exterminate THOUSANDS of filthy aliens), do not look any further.
I quite enjoy these games, the music is great, there are waves upon waves of enemies to mow down and it is just a joy to play a few rounds to get rid of some aggressions. It is nothing you would play for hours on end, but ideal for short play sessions.
This new game is a bit of a mix between tactics, shooter and tower defense. Enjoyable level design, lots and lots of enemies in different varieties, different soldiers and upgrades to unlock and the possibility to play through the different missions in several difficulty levels with different types of challenges adds to the replay value.
This is a guilty pleasure.

Since I have bought the game on release day, I also found a few bugs (I have already reported them in the discussion section under technical problems) but I am confident that they will be fixed, since I own most games from Sigma Team and I have never been disappointed by this developer.

So yes, I recommend this title, but if you are afraid of bugs (of course not the ones you shoot) maybe wait a bit until they are fixed.

the games not bad but also not all that great. gameplay is like plants vs zombies but instead of standing around you'll move forward on level, you'll use ore instead of solar energy to spawn units and have less variety of said units. beating levels gets you stars that will unlock more units and points used to upgrade them. you can have some fun with this but it feels like a budget game so here's some pros and cons.

+ 8 units that unlock when you get X stars. each has a passive or active (click to use) ability. characters are: miners (mines ore & will gather ore over time you must collect), shooter (uses a rifle & grenade ability), sniper (long rand with a passive "blasting bullet", i think it makes them explode on contact? the game isn't clear), medic (heals units 1 hex away and can boost their power), flamethrowers (torch things at close range & have a fire ball ability), defenders (use a shotgun & have a shielding ability), racketeer (shoots rockets at assigned targets only & has a drone that will bomb the field), and the elite (shoots lasers and can overcharge to do more damage)
+ you can upgrade each units hp/main weapon/ability
+ 14 spaces to place units. you can sell damaged units for a 50% refund.
+ 20 levels on 2 worlds
+ you can click on things to have your units focus their fire.

- you need to do each mission 3 times for the 3 stars. once on each difficulty. you can't just beat hard and get 3 stars.
- some missions will need one kind of unit you do not have yet. forcing you to redo old levels for stars or to power up existing units. it starts as early as level 3 or 4 as you HAVE to unlock the sniper before you can complete the level.
- only having 4 slots for units limits creative teams. you have to take the miner, you'll need a front line dps/damage sponge, a long range unit is a must, and you may want the medic. now you may think you can just swap out a stronger ranged dps or front liner but the later units costing more will come into effect here. you will either have to use the cheap shooter unit (no medic) or hope your miners can get enough ore to place units before you're over run.

Acceptable game for the price! Actually, it's fun!

This is not a pretentious game, the developersand designers give what they offer: a nice atmosphere, plenty of aliens to shoot at, upgrades for weapons and for the classes of different soldiers you may use to achieve the missions' tasks, and...loads of shooting action.

Graphics are and look ok and the game runs smoothly. Music is good but quite repetitive. Controls are simple to use. Although your men shoot automatically in a more or less acceptable way, some extra aiming and a good distribution of your men's classes are necessary to get the best offensive-defensive performance possible.

AH2 doesn't have, nor pretends having, a solid story line, not even a shallow one. Before each mission, you have a breifing informing you what's going on, what your goals are and that's it. Equip or upgrade your attacking group as much as the collected money allows you to, and go to kick some alien butt...or get your men dead trying.

As one of the people who sent a previous review said: this is not a game to spend long sessions of gaming, just play the game as a time waster and having some fun at the same time. It's a good game to play before or after playing a heavier game, or when you have nothing better to do.

I recommend the game for those who are fans of non-stop shooting action.

Another good thing about the game is that every level starts with certain achievements with an easy rate of difficulty, after you complete the level, you may go to the next one or you may stay there in which case you will have to complete a set of different achievements but this time with medium difficulty...then you may repeat, if you want, the level with harder difficulty and harder tasks. This repeat-the- level issue is useful in order to get more money to upgrade your men.

I know this system has nothing you may call "a novelty factor" but at least you are not going to suffer the frustration of getting stuck in a particular level having to repeat it forever.

Well, that's it :) !

Good game, funny time killer, but still not recommended - the game has serious bugs (i.e. special attacks don't work for some units), but looks like the tech support is stopped, so, these issues will never be fixed.

Pros:
+Graphics
+Nice gameplay

Cons:
-Except grinding, where upgrades cost too much, after doing all the side tasks in every mission you still won't have enough money to buy all the upgrades
- Even more buggy than recently released AS2 TL
-Difficulty balance, some missions are easy other becomes very hard

The last good game from Sigma Team was Alien Shooter TD, after that they has started to release too buggy games releasing one patch max two and abandoning them.

Ahh Sigma Team Inc. I had hoped you would have learned from the first Alien Hallway and made apropriate changes for the sequal. I still recommend this to anyone who enjoys simple strategic combat games, but it still suffers from a couple things that I didn't like from the first Alien Hallway -

1. The game, again, inevitably turns into a grind. Maybe they force this to extend the length of the game, but it's annoying. You must replay older levels over and over to gain enough gold to upgrade your units so you can complete harder missions.

2. No hotkeys. This was a nuisance in the first game, having to manually click and drag to summon units and, unfortunately, this returns in Alien Hallway 2. How hard is it to make solider slot #1 bind to the '1' key? I shouldn't have to click and drag in a game that demands quick reflexes to save your soldiers from exploding in fire and acid.

I have a certain love for Sigma Team Inc. because of the Alien Shooter and Zombie Shooter series', so my opinion on this is higher solely because I like the developers. I just wish they would make the necessary QoL adjustments to their titles and make them even better than I think they already are.

Also, being able to change your money and score in the save file is a bit silly but it's a single player game so that's not a big deal.

1) It Is hard, you can play all stages at easy-normal-hard and 2 units will be not level up at all... No credits.
2) It Is to hard (not possible) to play at easy. The monsters get stronger but no credits to level up your units.
3) Only 20 Levels!!!!!
4) A really good game, really nice view, really good game play but the worst upgrade system price that can be

Alien Hallway 2
pros:
fast game with modern day graphics with easy controls that moves from location A to B to C and so on,
good amount of action and special effects,
cons:
some difficult battles.
grindfest (It takes alot of resources to upgrade and unlock new unit types.)

good game.
Personal Suggested Purchase Price: $0.49 Or Less During Sale

Generally a just-so-so game.
Most of the gaming experience is good. In this game as a squad commander you arrange different classes of soldiers in a group, activate skills when needed, focus fire on tough target... after mission you do some upgrades.
However, some game balance is not really reasonable.
I recommend purchasing this game when it is on discount.