To easily get the combo bonuses, use Letter F and balance on the front wheel for as long as possible. (Don't pedal while doing this, only balance leaning forward and backward.) Even if you aren't moving, it still registers as a front wheelie, and you can rack up an easy 5x combo for the achievement. (+) to keep this showing!
Great game so far! Sidenote: Level 8 reminded me of the levels in Super Mario Sunshine where Mario loses FLUDD and has to make it to the exit without his main platforming abilities.
Completed again. It was definitely much more enjoyable this time. It was really fun, and I hope to see a flash version for the second game. (the one that will actually be a game instead of an experiment)
 "Vector Stunt"){kind=icon}
 "CycloManiacs"){kind=icon}
 "Papa's Freezeria"){kind=icon}
 "Soul Tax"){kind=icon}
 "Not To Scale"){kind=icon}
 "Sarah's Run (preview)"){kind=icon}
 "Cat God vs Sun King"){kind=icon}
 "Legend of Kalevala"){kind=icon}
 "Spewer"){kind=icon}
 "The Fancy Pants Adventures"){kind=icon}
 "Bullet Heaven"){kind=icon}
 "Run 2"){kind=icon}
 "Solipskier"){kind=icon}
 "Power Tank"){kind=icon}
 "Bubble Tanks 2"){kind=icon}
 "Continuity"){kind=icon}
 "Portal: The Flash Version"){kind=icon}