Like many others, I really like this concept and the execution was somewhere between "challenging" and "slow down it's too difficult too soon!". :D
My anonymous co-reviewer said: "really cool concept, difficulty/speed/progression could use some work".
The combination of repetition and ability to supply custom levels makes me curious if there's potential educational applications here (e.g. via "spaced repetition") and what other text-based media might work well for levels (e.g. Tweets? The "classic code" mentioned below? News articles? Classic poetry/literature? Text books? This comment?!)
Definitely a cool entry.