Well I will not lie, the game is not good, but it does not mean anything bad it is amazing that you managed to make a whole game in 48 hours !.
Here are some improvements for the future:
1. The music is too loud even when you lower the sound on the computer it is just too loud.
2. When I shoot there is no projectile or anything I just hear sound and it is not epilating at all.
3. The graphics do not look the best, now I am not a designer at all I hardly know how to create a cube in a blender but you could invest a bit and take a model from the internet or use a free texture for lava.
4. It's not clear to me what I need to do I just start and there is lava underneath me and I guess I need to jump from platform to platform but for what the rifle and also why jump I see no purpose.
5. When you die you get a lousy picture you took from the game of Game Jam and you can not restart at all.
Hope you learn and get better !.