Any game jam is a tricky challenge for a game designer, as you have to build cohesive gameplay in concise terms. As a result, you can make some mistakes which can ruin a player's experience. And here is some advice from me about jam game design.

1. Think about a core loop. Determine a core gameplay loop for your game and draw a simple flowchart of it. It's a usual thing for experienced game designers, even with a lack of time it can make all the difference, as you can see how your game should be played.

2. Set priority for all features. Prioritize your game features and systems through onion design pattern.

3. Stay focused. Focus on your key features, make them smooth and entertaining. Don't rush to implement additional mechanics, without a good core loop they won't work correctly.

4. Ask for help. If you are in a dead-end and can't make head or tail of how good is your idea - ask your friends and other participants of the jam, it's not a competition, help to each other.

5. Make it simple. Don't rush to implement art, take your time and make sure your idea works as intended with simple sprites. Yes, visuals are essential, but smooth gameplay is more significant.

6. Work with balance sheets. Make simple balance sheets for your game. They can save your time at the and of the jam and also facilitate your game balance process.

7. Play your game. Play your game and make balance adjustments, as I said before, even a jam game must have a smooth and enjoyable core gameplay loop. You can achieve this goal only through playtesting.

8. Enjoy the event. Relax and have fun, this event is about making games, not about winning the victory!