Recs.
Updated
Risk of Rain is an indie action platformer with roguelike elements that costs $9.99. With permanent death as a primary feature, players will have to play their best to get as far as possible. Fight on a mysterious planet with randomly spawning enemies and bosses, either alone or with 3 friends in online co-op.
SpecsUpdate
Pros
Pro Time equals difficulty
It gets tougher as time passes by. That means by minute 40, you are playing at hardcore difficulty. This makes for an experience that is good for learning the mechanics as once you can not advance due to the difficulty you will die which means the game has to be repeated which help learn the ins and outs more and more each time it is done.
Cons
Con Power-ups are not shared
The power-ups you pick up/buy in-game are not shared between players in co-op. It usually ends up being a race to see who can grab the power-ups first. This tends to make it unbalanced in the favor of 1 player having all the power ups, and doing everything themselves.