Going fullscreen actually scales up the view so I can see way more. This is probably a balance issue, because that means people with higher resolutions get to see more game.
The control scheme is crazy. Mousing over items then pressing space to buy them? Repeatedly mashing up arrow makes you go WAY higher? I'm having to move my hands from the arrow keys to the mouse to the spacebar, and I only have two hands.
Respawning coins right next to the pad removes the incentive to take risks, but without them, the game would be impossible. Also I can hop in the ocean to make then respawn?
Note: Pressing down when not on the pad makes the menu flicker.
There's a good game idea in here -- reminds me of Motherload, an old flash game. But it needs refinement. Discoveries in the sky, platforms, better controls, etc. Go play that game for inspiration if you need it.
I explored to the top of the skybox, and visited the sides of the map before deciding I had seen everything in the game. I do really like the simple pixel art, by the way.