I have to say, if this is your first finished game, you've got some pretty strong design and dev skills! Everything worked perfectly and the goal of the game was clear, controls easy to pick up. So good work on pulling off that much already!
As someone who also worked on an "endless"-type game for this jam, I know the main design pillars of these games is rewarding mastery and encouraging replayability. One of the ways to do that is through high difficulty, and that's a tough design goal to nail down. While playing your game, I quickly decided that I wouldn't bother trying to collect coins or anything else, because it was nearly impossible already to not touch the walls and die instantly. My strategy wasn't "See how high I can score," but rather "See if I can live more than 10 seconds".
I'm not sure if that was your goal, but it was discouraging to have a single hit restart the level every time. I'd suggest giving players a little more room to make mistakes, especially in the very beginning, or even turn the walls into something other than instant death. Seeing that this is a prototype, I wish you the best if you choose to finish it. You've got a great starting point!