Some of the effects were hard to understand. I'm not sure when an enemy's strength would be 0. I mainly just picked things that would deal damage, then used the card on whichever enemy was attacking that I thought I could one-hit-KO. I got to room 8.
Also this error came up. Just looking at it, it probably was the result of more attacks after my character died.
Error
enemies/basic.lua:11: attempt to index local 'player' (a nil value)
Traceback
enemies/basic.lua:11: in function 'func'
enemy.lua:33: in function 'play'
room.lua:62: in function 'nextEnemy'
room.lua:55: in function 'func'
lib/closure.lua:4: in function 'delay'
room.lua:94: in function 'update'
game.lua:17: in function 'update'
main.lua:104: in function 'update'
[C]: in function 'xpcall'