C'est pas mon type de jeu.

Nice isaac clone. It's been done with gamemaker studio, the result is quite impressive.
Don't be fooled by the cute characters, it's devilishly difficult.
Perhaps it's easier in multiplayer (if difficulty / enemies do not scale), I've played it in single player.
It has a nice mechanic where you pick up items that give you various penalties and you can barter them at the shop for artifacts. This makes the game a bit unbalanced though as shops pop up randomly and you can get too weak at times, with no shop in sight, or worse, a boss next. For that, it can be slightly frustrating.

perfect balance between fun and difficulty
great modding community too