Excellent premise, crippled execution.
This seriously would have been perfect had it not been for some awful bugs.
1. The lepers: At your starting speed, it is literally impossible to catch up to them, thus if they spawn frequently enough it is possible to never get the combo needed to increase your speed.
2. Birds + Trees: I didn't have an issue hitting the trees or the birds separately. However, when they spawn in the same spot (particularly when it's on the other side of a gap jump) then it's a serious problem. Because of the nature of your attack and the height distance between the two obstacles, you can only hit one of them and then you are stuck slamming into the other. Maybe if they only spawned together on the rarest occasions it'd be less an issue, but within 5 minutes of me playing this happened on about half of my runs.
3. Aiming: The aim for the spear isn't 1:1. I get that you probably wanted to limit how far up and down we could go, but it's far too easy to end up accidentally moving/clicking the mouse way off screen just trying to aim/attack. This needs to be addressed in some manner.
Other than those issues, I really dig the game. Love the music, the character design and the idea behind the gameplay.