Ghost Ninja

Ghost Ninja is a fast survival game set in an arena that keeps filling with ninja enemies. You move, dodge and slash your way through massive hordes, collecting gems as they drop to unlock upgrades between the waves. The reason runs stay interesting is that the game does not hand you the same build twice — new weapons and abilities arrive as you progress and stack into wild combinations, so the way you are fighting at the end of a long run may bear little resemblance to how you started it. Because the control is a simple click-and-drag, all of your attention goes into reading the swarm rather than managing inputs, which suits the pace it runs at.