I'm super impressed reading that you developed this on your own! I think there are some really nice touches to it, such as the smooth transition to black with the spare/kill instead of just cutting to them. The ending screens were a nice addition as well! I managed to get four of the endings but I don't know if I missed one of them.
Apart from some of the endings only playing music in one ear of my headphones, it worked perfectly as well, nice work!