This was fun. I really like the retro style graphics and it brought back some memories! I also really liked that you put some verticality into the level design to keep things interesting.
A minor thing that made me restart the game on my first try was that the scene transition when i went through the first door made me think the game had crashed. May be it's shaders loading for the first time? A loading screen could help with this! I am playing in the browser in case that helps debug.
Other than that, i enjoyed this one. Good work!