Interesting premise but the main appeal of plinko is where the ball lands at the bottom. If you somehow segregated the bottom of each section and provided rewards based on that... it could make it more interesting. (x2, x3, x4, x5, x4, x3, x2)
Graphics leave a lot to be desired. Audio too. Overall it's a good prototype but you should flesh it out to increase engagement. Also your ad system is not working whatsoever, but personally I find it annoying anyway.