flappy plane

dev log: 

update 1.0 (first release): contains a minimal flappy bird game but with a jet.

update 1.1: added coins, and a shop that has no use in update 1.1.

update 1.2: added better difficulty ramping, 

new plane sprite, a shop that actually does something, 

 and coins get added as you go instead of all at once when you lose.