1 min challenge, means that you have only 1 minute to pick up all the diamonds and run to the exit. There are some 1 min challenges and some 30s challenges. One of my favorite games on Commodore 64 is the Boulder Dash series. This is the Construction Kit, where you can make your own maps to have fun on. I would make many maps, some fun and some probably not so fun or good. If you want to try them out, you can download the game (.d64) with all the maps on: (dropbox) and everytime I make a new map, I will upload to the same folder. Sometimes I would make a new video with on of the new map I created. It is recommended to use a digital joystick to play old computer games on both C64 and Amiga, and I use the good old Competition Pro with and DB9 to USB-adapter bought at ebay: He makes them himself and ship very fast (5 days to europe). I would also recommend buying the Cloanto C64 Forever and Amiga Forever
