Writing slow code that works is mostly fine. Writing faster code is better. Writing the fastest code ever? Awesome. JOY OF PROGRAMMING is a single-player experience you play at your own pace and for your own learning and satisfaction. Nevertheless, comparing how well your solution works relative to others' can be quite interesting and provide further insights how to improve.
Once you finish a level within the game, you will see a minimalistic histogram that tells you how the performance of your solutions compares to those of others (anonymously).
You'll see a comparison with different metrics such as processing time, memory usage or lines of code. If you ever played any of the Zachtronics' games (highly recommended as one of the inspirations for this game and particularly the histogram feature) this will be immediately familiar.
I'm thinking about further ways to refine this feature such as filtering the histogram to a peer group (those with similar programming experience), visualizing joint distributions (e.g., code that minimizes both, space and runtime requirements) and eventually an optional public leaderboard.
As always, Happy Coding.