Not bad!
I managed to run out of ammo though, and it was difficult to find more. Health pickups respawn almost instantly, but ammo either doesn't respawn at all or respawns too slowly. Maybe spawn some ammo instead of the killed enemy?
Also, I think abilities are not communicated to player good enough; when you pick up an ability, it's not displayed anywhere until used; and it's easy to forget which card meant which ability.