Mini Solitaire Battle Mechanic

Long time lurker, first post. I'm working on a two-player eurogame in which players try to build towers level by level. They get money by playing quick solitaire games, a dice game and a battle game. I may add a memory-type game later. My problem is this: I'm looking for some sort of simple mechanic by which a player can quickly battle some kind of NPC, with some sort of movement and the possibility of buyable weapons, etc. Any suggestions, or games which use something similar that you could point me to? Either would be much appreciated. Thanks!