Plan for day 23

1. Fix traversal performance. Currently it's 60x slower than du. It should be as fast as du. And, god help it, I'm fully prepared to use du to do it.

2. Profile memory use. Optimize memory use.

3. Add a funny dot to the top-right corner of directories. To make them more nu.

4. Skip jogging and do indoors exercise instead. (Walked an hour in sleet rain yesterday. Today it's -2C.)