A nice start
The game in it's self was too easy and very short, and a bit longer of a game would be appreciated. It took me 3 tries before I realized the spike could be walked through and to pass that darn cute spider. Also, there were alot of moments where it just.. froze in mid air or something, one time I encountered a glitch where there was the text from the sign selling Razors and a floating bush. So the 'error' button was a good idea, but you really should try and make a save system or checkpoint instead or to be able to speed through by means of button.
Though I have to disagree with Paint It Black as an 'emo' song, but otherwise a nice track. More transparent spikes, don't give hints on the boss (natural human instinct to press the giant red button), and maybe the boss could bounce around aimlessly instead of up and down. A health bar, crouch option, and to change direction while jumping in the air might be good ideas. Hope this helps!
4/10 for a good start to a game and for the flowing animation.