I've often wanted to participate in a 48-hour game jam but have always been to sleep-deprived or busy to actually do it. Yesterday, a friend at work challenged me to make a game in 10 minutes. This is a far more reasonable amount of time to allocate to game development so I accepted the challenge and set myself the following guidelines:
The game must be a game in a vague sense; it must have a clear goal which can be attained. This was one area where my previous game jam fell down.
The game must be feature-complete; all the gameplay elements I plan to include must be included in the first pass.
Graphics and sound are low priority and can be added later. They just need to be at a functional level so you can tell what's going on.
As it turns out, 10 minutes is an unreasonable amount of time in which to make a full game so it spilled over to the 30 minute mark. Still, I met my goals, and the game is winnable with a vague sense that you could have done better if you tried a bit harder next time.