When I picked up the gem for the first time and saw the lava I immediately hit shift to try and run. I also hit control the first time an enemy shot at me. Crouch and Run would be awesome. I understand the no running when you get the gem as it looks to slow you down.
I also couldn't find a way up before the lava hit me and then passed by. It doesn't seem like the whole thing causes damage, so I survived until it passed me by.
I really liked the sound effects. The one where he said oops made me chuckle.
Good job!