ok, really really stylisch gameplay, in theory. i think you should ad a text next to the + Buttons, for example something like "jump" "change direction" "run" to even let the player understand how the controls are working. i nearly quit the game before even understanding how it worked. in the end i managed to get through the first level, with a little bit of luck and 5 red rubis to jump over both obstacles.
i think if you add music, sound effects and maybe a tutorial this could be a unique game.
maybe i miss something because i did`nt finish it, but how is this matching the "underneath us" topic?
But still, well done!