- Distributed file systems with unreliable networks or no network at all.
- Multi-master file synchronisation
- Windows Presentation Foundation
- Pentominoes and exact coverage puzzles
- YAML and other human-friendly, machine-processable file formats
This also explains why I write my own software to exactly match my needs and why I get so discouraged when I need to find workarounds for bugs or limitations in the frameworks or hardware I use. It's not interesting or fun to try and trick the computer into doing what you want. Only occasionally are the limitations part of the puzzle.
Mokalus of Borg
PS - The tough days are when my work is much less interesting than these puzzles.
PPS - The only classical "puzzle" here is pentominoes.