Back in the good old Commodore 64 computing days, there was a great game called Boulderdash. In the game, you ran around an area collecting diamonds while avoiding being crushed by rocks. There was also a timer and an exit to each level you had to reach before the timer ran out. Boulderdash is not available now except using a C64 emulator (which I’m going to try for the heck of it), but there is an open source version called Rocks ‘N’ Diamonds which seems to be a nice successor.
I have not put much time into the game myself, but my younger son is very into it right now. I recently gave him my MacBook, on which I left a Fedora Core 9 VM for him to play games, and after finding the game he’s been hooked. I figured there was a better way for him to play besides running FC in a VM every time and sure enough there is a Mac version of the game (as well as Windows, DOS, and of course Linux). If you like action games with a little bit of puzzle to them, Rocks ‘N’ Diamonds is worth checking out.