This was an absolutely charming game! I loved everything about it. The style, the music, the sound effects, the gameplay... EVERYTHING! I would have totally played this on the Gameboy as a kid. What surprised me was how smooth it played. It felt very polished.
Some "minor" points of critique would be that it wasn't quite obvious what could hurt you at the beginning (you learn pretty quickly though). So, if you decide to turn this into a full game, you may want to think about how you draw the obstacles more. However, because of the way the game is designed, you may not want to. The level design introduces you to the concepts very well, so by the end, I knew what I was doing and what to avoid.
Overall, FANTASTIC job on this! Time well spent, and I would totally play this if you flesh it out more. Thanks for the experience! :)