Hydra Slayer
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).
The Steam version of Hydra Slayer includes online achievements and leaderboards, a “challenge” mode for short but very interesting games (much more unpredictable than the normal play), traps to lead hydras on, and Orbs which provide a powder/potion effect many times at the cost of a weapon slot!
Steam User 0
Hydra Slayer is one of those games that reminds you why games are such a wonderful medium for exploring ideas, challenges, and the endless possibilities of interactive entertainment.
At first glance, it may seem like a simple traditional roguelike about walking around, finding weapons, and fighting monsters. But as you spend more time with it, you begin to understand that there is something much deeper happening underneath the surface. The game constantly encourages you to think, adapt, reconsider your decisions, and approach familiar situations from a different perspective.
The combat is especially memorable. There is a certain elegance in the way every action feels meaningful, and the simple act of attacking can become a small intellectual exercise. Instead of simply asking whether you are strong enough, the game asks whether you understand the situation well enough. This creates a very satisfying connection between strategy, experimentation, and the gradual development of your own understanding.
And this is where Hydra Slayer really shines. It does not constantly tell you that you are becoming better. It simply puts another situation in front of you and lets you discover that you are now capable of solving something that previously looked completely unreasonable.
The roguelike structure works extremely well with this philosophy. Every run feels like another opportunity to learn something, make better decisions, and discover another layer of the game's systems. Even failure has a certain value, because it leaves you with knowledge that can be carried into the next attempt.
There is also something strangely satisfying about the whole concept. The game takes a very specific idea and builds an entire roguelike around it without losing sight of what makes the genre enjoyable in the first place. It feels experimental, but not experimental for the sake of being different. There is a clear sense of purpose behind the design.
I also appreciate that Hydra Slayer respects the player's intelligence. It doesn't need to constantly explain why something is interesting. It gives you the tools, presents you with a problem, and trusts you to figure out what the game is trying to say through its mechanics.
After finishing it, I was left with that rare feeling that I had not simply completed another game, but had actually spent time engaging with a genuinely unusual idea. And ultimately, that is probably the greatest compliment I can give a traditional roguelike.
Highly recommended for anyone who enjoys traditional roguelikes, puzzles, strategy, experimentation, or games that are willing to be a little different.
A very good game, and, in its own peculiar way, a very good reminder that sometimes the most interesting adventures begin when you stop asking how powerful your character is and start asking whether you have understood the problem correctly.
Steam User 0
I knew math class would come in handy someday