The use of background asset and sprites aren't very good. The wall in the foreground is as dark as the tree silhouette in the background and sometimes I mistaken the actual floor and the floor in the background making me fall to death many times.
The movement isn't too good. It makes the chance of avoiding spikes very low. It also makes the feeling of the player is being near danger all the time.
The assisting and feedback aren't enough. In continuous event there is no pausing and there is very little informing.
I can't tell if the difficulty curve here is appropriate. But the game is hard.
Anyway, good job. Those mechanics seems hard to get it right.