Risk of Rain is an action-platformer with roguelike elements, with some interesting mechanics wich I'll try to explain the best I can.
Even if you start with only one playable character, there're ten of them total, and each one plays differently, thanks to his own four attacks.
As time passes, difficulty will increase and enemies will spawn endlessly until you find the teleport, wich makes you fight for one last endurance round; beaten that, you can advance to the next level. Like other games of this genre, you can find active/passive upgrades (like piercing shots, increased defense, missiles and so on), but you can level-up too by collecting experience. An interesting fact is that powerups do stack, so you can have increased effects by collecting more of the same.
Once you've completed enough levels, you can choose between replaying them to gain more loot, or going to the final one; you can easily grind more powerups if you want to, but the game can be beaten in less than a hour in a good run.
Bear in mind that this is the kind of game where things get bad pretty fast, and you have to start all over again.
Pixelated graphics are really good, but sometimes the action on screen become a little too chaotic. Chaos apart, gameplay is overall pretty much solid and fun.
The game's soundtrack is AWESOOOOOME, I love it.
Also, this game has coop, playing with other people works well and in my opinion some classes are not meant to be played alone.
Reccomended if these features caught your attention, and/or if you have friends to play with.
I don't think Risk of Rain is a masterpiece, but it's a really solid game.