For now it's too simple. Got 1k point with no problems at all and ended run by my own. I'm pretty sure you can add some variety to this formula. Maybe gradually reduce cooldown of enemy spawn. Or add more enemies, like the one who teleport to the mirror opposite side of the field on blink.
To the minor thing, but strange things:
1) Sword swing sprite same no matter to which side you are facing and that feels wrong, especially when you face left.
2) You can swing up and down only on the move, if you stop, hero starts swinging only to the side, even if it was facing up or down.