This game is now available on Steam!

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Hydra Slayer
Genre: Strategy, RPG, Puzzle
Platforms: PC, Mac, Linux
Languages: English
Players: Single-player
Feb 7, 2015 @ 3:21pm
Mar 24, 2016 @ 11:00am

View Hydra Slayer in the store

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Hydra Slayer released today!
You are facing a nine-headed hydra. Your flaming longsword cuts five heads in each swipe (no more, no less), which will kill a five-headed hydra, but a larger one will regrow two heads after each swipe. Your storm scythe cuts exactly seven heads, but it makes ten heads grow back if the hydra is not dead. Is it possible to kill the hydra? What if you also had a silver dagger, which cuts just one head, but makes five heads grow back?

Solution: It is impossible without the silver dagger (the number of heads always stays divisible by 3), but possible with the silver dagger, for example: 9 -> longsword -> 6 -> longsword -> 3 -> dagger -> 7 -> scythe -> 0.

If you liked this puzzle, and you also like dungeon crawling, Hydra Slayer is for you!

Hydra Slayer is a roguelike (randomly generated dungeon crawler), with unique combat mechanics based on the puzzle above. It is challenging both at a short term tactical level (each hydra is a unique challenge, bumping into it with your weapon almost never works), and at a long term strategy level (you have to build a set of weapons which slays hydras effectively). While the early levels could be used to teach arithmetics and tactical planning in a fun way, building an effective set of weapons for late levels is a challenge even for expert number theorists!

Hydra Slayer currently features a tutorial, 5 player character races with distinct characteristics, 28 enemy types (10 common hydras, each in two varieties, and 8 special enemies), 28 types of equipment including rare artifact weapons with special properties (not counting material and size variations), 15 weapon materials, 18 types of magical items which help you in your quests, three game geometries to choose from, 8 level topologies on very deep levels (including the Möbius strip and Klein bottle), 11 level generators, and two endings (a small victory for quick challenges and more casual players, and a big victory for those who want more challenge).

Hydra Slayer is available for free from its website[]. The Steam version will add online achievements, leaderboards, trading cards, and the convenience of Steam. See also my other game, HyperRogue, which is already on Steam! While both games are based on mathematical concepts, they are very different in nature.

The second screenshot shows the optimal strategy (sequence of weapon attacks) against a 105-headed golden hydra, at some point in the game (level 11). If this looks too difficult for you, note that the game starts much easier (new weapon types are introduced gradually), and you don't have to always use the optimal strategy to be successful :)


Originally posted by CGGreatHouse, MyMathForums:
OK, it's probably not number theory, but it is awesome. Thanks for releasing the source (so I can run it on Linux). I'm on my third game, the first game consisting of me dying before I could properly see what I was doing.

Originally posted by William Graber, review on Google Play:
Difficult, but worth it. Great game! Very unique and interesting mechanics. Definitely not for the faint of heart (or mind).

Originally posted by BDR, Attnam IRC channel:
Also you know you're playing a funny game when you make your opponent stronger so he's easier to kill.
Popular Discussions View All (1)
Feb 9, 2015 @ 1:22pm
Adam Salami
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vo3435 Feb 26, 2016 @ 2:15pm 
Wow, it's greenlit! Totally amazing!
OgNimaeb Dec 29, 2015 @ 1:41pm 
I'm a bif fan of HyperRogue, and I love the idea behind this one. I can't wait to see it released! :)
bug_sniper Nov 28, 2015 @ 9:39pm 
Upvoted, glad to see this finally coming.
Conan the Librarian Nov 11, 2015 @ 10:00am 
Upvoted, heard nothing but good about this at roguetemple
CodexArcanum Nov 9, 2015 @ 10:34pm 
After seeing how much better HyperRogue got after going green (and it was already incredible before) I can't wait to see what happens with Hydra Slayer after it goes big!
SheepsTooth Nov 4, 2015 @ 12:38pm 
Voted. For the graphics haters: You can always play in ASCII mode ;)
루케테 Nov 3, 2015 @ 7:06pm 
vo3435 Oct 26, 2015 @ 4:18am 
Roguelike or puzzle - what is better? The answer is: puzzle roguelike! Thumb up.
The sap is rising! Oct 23, 2015 @ 2:11am 
If you don't "get" roguelikes or they aren't for you don't worry. We can try to still respect you and your opinions; it's hard but we'll try our very best. You must understand though that you do have a disability and at times our patience while caring for you will be stretched very thin so apologies in advance for the times when something snaps and we scream at you.
LootenantDan Oct 1, 2015 @ 7:07pm 
I agree with Plinky the graphics suck more effort should be put into this, there is no lack of excellent engines that can produce better quality than this garbage.