Man that was difficult, I did manage to beat it though. I suspect a lot of players will not get past the first spider or the spiders combined with 'falling things'-obstacle.
Also, those blocks that turn on/off when you jump were confusing. At first I thought that they changed based on time intervals.
The obstacle that slowly disappears and reappears was pretty neat. It made for an interesting level, in which you needed to influence the level to get those projectiles across.