Bug Report:
Not sure how much support you plan, but thought I should report this.
On the screen before going to the jumping demon, if you head to the left instead, there is a bird on the top wire of two telephone poles.
If you shoot through the bottom wire, and hit it without breaking the second (top) wire, you can then repeatedly shoot the same spot where the bird was and farm gems from it. You can beat the game with just this bird.
From my testing it won't always work, as sometimes the first shot breaks both wires, but if the bird dies and the wire remains you can farm piles of gems.