I'm too lazy to read all of the suggestions
So I dunno if it's been written, but I'd like to suggest a time limit themes.
1st one is to build a map up to 30 seconds.
2nd one - build a map longer than 2 or 3 mimutes
And the 3rd one came to my mind. Use only 2 buttons to finish the map.
All the themes've been used in TMU for sure