The effort went into what's really important - clever puzzles (and 45 of them, are you kidding me?!). Some of those are suuuper tricky (especially when it's obvious to avoid low hanging fruit of pluses next to starting position, since those could make it impossible to fit in some places). Really cool.
Now, for some nitpicks (because I really think that the game itself is great the way it is, those are just small things that annoyed me a little bit, also a small disclaimer - I didn't finish the game, there's just too many levels :D):
- The fact that there is a restart button, but no undo button. A lot of levels let you intentionally soft lock into a shape that will just not fit the exit, and that's cool. However, when you realise this, you have to repeat the same sequence from the very beginning and it became a bit tedious, especially at longer levels.
- I'm not a fan of locking levels behind stars like that (especially in jam game, since I just want to see later levels, if only out of curiosity :)).
- I don't see how those levels with red-spiky-things add anything. You still need mostly "perfect" runs to unlock starts and for most puzzles the optimal route is the only route anyways, so being forced to start over because of one mistake just didn't feel right (to me).
Ok, that's enough. You said in the description that this is your first game. It's a phenomenal entry to the jam and a fantastic puzzle game on it's own and you should be incredible proud of yourselves. Not all of us are talented enough to start with such a banger and I will definitely be waiting for your next one(s), cheers!