Yes, resizing Shyguy surely helped.
The distribution of coins is much better now and the splatter effects are finally visible and bloody
The new soundtrack is also fine though I also liked the first one.
Only minor criticism is the collision area of Shyguy: it's too big!
Make it a bit smaller than Shyguy itself, around 80% (seems to be pretty common).
And the tunnel/cave itself: the amount of getting narrower or wider - is that totally random?
It should get narrower the further you progress into the caves. And maybe add an exit to the tunnel to show some scoring - and then continue with the next tunnel with more enemies, more speed, less coins, other obstacles. You'll get the point
Ooh, and one issue about the smoke trail: Add some fire as long as you press the button to give the illusion of firing the jet engine...
It's getting along nicely - I needed to rip my son from the first version and hope he doesn't see me playing the future versions