Surprisingly fun! Very good for your first jam!
It was a little hard to collect the heart containers.
I see what you tried to do with the enemies. The proper way would have been to generate voxels, but this isn't exactly beginner friendly.
A reload button should always be included in the build! Sure the browser reloads it for you, but this is much slower. This is probably the easiest thing you could improve.
Btw it is normal to not use up the full 48 hours.