Very neat deconstruction of different types of rewards/challenges.

I found an infrequent and difficult but large reward (triangle), more frequent but easy (circle), ones the player needs to chase (rectangle), easy but short-lived (square zones), an exhaustible safety net (pong paddle), and a smaller permanent safety net (proximity to spikes). I especially like how the last one is tuned to save the player from death in every case except the one where he or she is totally screwed.