Nice concept
I liked the idea, though I noticed a small glitch. Occasionally, the player character gets frozen where he stands if you move while throwing the boomerang. I tried to replicate the bug a few times, and while it doesn't always happen, it tends to happen more often around level 4 than the earlier levels. Normally, the character will temporarily freeze while the boomerang is flying, and in this glitch the boomerang doesn't fly, the character is frozen in place holding the boomerang. Hope that helps.