I envy the control of the scope this game appears to have given the game jam setting. For sure, that is one of the things that I struggle with in a game jam is knowing what features to add in the condensed dev cycle. It seems like the core gameplay loop of your game is very solid and after achieving that loop, you could add additional features to enhance the game. The full game experience felt very polished and it felt like it provided when it promised on all fronts.
Loved the music, it was very fitting given I will explode in ten seconds if I don't touch a green gem.
A couple pieces of constructive criticism:
The green arrow that tells you where the next gem is located is drawn underneath the tiles, so sometimes it is obscured when the gem spawn below you.
Also regarding the arrow, it disappears when you are close enough to the gem, however it seems like the arrow will go away before the gem is on screen and my brain is not smart enough to connect remember where the arrow was pointing. I think in general it is a minor gripe, but I think it often costs me some time which is heartbreaking in a time based game.
I also got a high score of ten with Bitboy and I am not enough of a sadist to try that with jankman.