Thanks for playing!
I had a lot more planned for the game, since I'm used to week and month long jams, so time time limit caught me off guard. Maybe I'll come back to this at some point (probably not though).
The height of your jump does actually depend on how long you hold the space bar. If you're still ascending and release the space bar your vertical velocity is set to 0. It's just the jump is rather fast, so it's easy to miss.