> are all usually quite polished given the timespan
The open secret is that they might not start coding or building assets until the start time, but they have spent a lot of time thinking about the ideas before then (even when the "theme" isn't known before hand people tend to make ideas fit theme with tweaks), which just speaks to the "code is not the bottleneck" thesis.
Game jams typically require games to adhere to a theme that is only known the day of, and the best entries will make a game specifically around that, not just adapt some pre-existing idea to it.
The themes are so open ended it’s very easy to adapt most game ideas. Games that win tend to be the most fun to play not necessarily the ones that fit the theme the best.
The open secret is that they might not start coding or building assets until the start time, but they have spent a lot of time thinking about the ideas before then (even when the "theme" isn't known before hand people tend to make ideas fit theme with tweaks), which just speaks to the "code is not the bottleneck" thesis.