Not a bad game! Risk, reward mechanic makes it more fun than your typical games of the genre.
Then again, it could use some more work - if you continue the work on the game in the future, you could make a more interesting background, some story maybe? thing like that. Some more lasting rewards would be nice too - scale the difficulty a lot, but scale the power a lot - that'd be very interesting, and give a greater feel of progression.
The game has a good promise though.
Best of luck!