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I have a tendency to spend a lot of time working on the mechanics of games, finely tuning collision resolution and other rules. There's a great talk on YouTube by Martin Jonasson & Petri Purho called "Juice it or lose it" which shows how much more you need than good mechanics to make an enjoyable game, and it's these things I need to work on.
The code is in my github repository "2dgames", under the directory "collector": https://github.com/jmacarthur/2dgames/tree/master/collector. You'll need PyGame to run it.