This is SOLID for a first game jam experience! The art and sounds were nice, and it felt like there was thought put into the design of the level.
At first I thought the amount of concepts being taught was too much, but by the end of the game, I felt like I had learned the language of the game and was swapping between the light and dark world and the past and present self as though it came second nature to me! It's a shame there wasn't enough time for more content, because I finished the game wanting more :)
A piece of feedback I have is that I wasn't fond of how the camera behaved. The way it lags behind the player made platforming feel kinda bad to me. I would have much preferred if it affixed the character to the center of the screen at all times, and maybe zoomed out a bit to help with determining where I want to go.