F12 does nothing. The game starts in its own window anyhow.
The exe version works for me!
So, about the demo:
The humanoids movement is pretty weird, both on the ground and mid-air.
The acceleration on the ground is somewhat slow, which often would leave me jump up instead of forward.
The wall jumps are very unsatisfying to perform as I feel like I have to press in the direction of the wall, which causes me to move towards the same wall I jumped off of AFTER I did the wall jump (due to air control). With the bees I didn't have much luck to dodge them.
Crouching in the air is a fun idea for a 2D platformer, but the hint should come before the pit, not after you already fell.
The spiders movement is alright, though the jumps with the spike blocks too tight, or maybe the collision of spikes is too big.
As the demo is focused on the movement of the 2 characters I'll leave it at that.