This is pretty good for being made in 48 hours. Good job!
The graphics in the interior sections are kind of monotonous (for example, almost everything in the cave is gray) but I like the look of the colorful exterior section.
Next time you make music, you should try using some standard non-percussion instruments, particularly for the melodies you did with pitched percussion. There's dozens that come bundled with PXTone.
Innominate, the collision boxes should not be substantially larger than the spikes. Each spike on the four way spike object has its own collision box, about two or three pixels short of the end of the spikes. There are only a couple pixels of empty space that are covered by a collision box, and I'm surprised you'd notice that. However, since you did notice it, I'll look into making it better.