Very hard, didn't manage to go far. Took me about 4 tries to figure that my hitbox is in the head, before that I thought the game wasn't possible at all. Some feedback when being damaged would be great (e.g. SFX and blinking snake's head during the i-frames)
Also, the controls were inverted from what I expected, so that also felt weird.
Anyway, congrats on making it through the jam!