Very new to this game, apologies if it's already been seen/in use.

While Reicha7 was helping me get into the game - by shear incompetence, I think I've found a skip in the red castle stage:

Instead of this:

do this:

Instead of jumping all the way to the right, shooting, dying and waiting. You can jump into the first spike, facing back into the block and let a shot off as you die. It lets you clear the block almost instantly, and respawn right next to the hole.

Not sure how reliable it is, but jumping into it instead of walking - seems to let you fall "further" into the hitbox = more chance your shot connects.

Anyway, hope that's a useful contribution - apologies if it's well known/used.