Very cool concept! And congrats on taking the leap into making your first game jam—huge accomplishment! I really liked the idea of using moving light sources and having shadow platforms only affect your shadow character. It's quite unique and well executed.
However, I did have some trouble understanding the solutions at times. My expectation was that my shadow would appear in the same spot it disappeared, so there were moments when I felt a bit confused about how to approach solving a level. On the last level, I think I just got lucky!
I also appreciated the little detail of having a jump button but no jumps ;D
Great work!