I ended up playing it twice, because whatever weapon you pick up replaces your old one, so I thought I was softlocked when I couldn't defeat that one enemy in the top world you need the gun for... Turned out it was just hiding a bigger gun and I'd somehow missed the roll powerup entirely.
It's a really good game! Good graphics and music, with a nice variety of power-ups and weapons and little sprite details. The player was a bit too floaty for my taste, causing me to bump into doorframes and such, but otherwise it seemed to play well.
However, I found a possibly game-breaking bug where if you go through a door that was previously locked, it unlocks the door again and you lose a key. I was so worried the final artifact would be behind a locked door because I died on the buzzsaw room and lost my only key going back. (Thankfully, that wasn't the case.)
So overall, great job!