New mode: Puzzle

Would be cool to have a mode that lets you play out magic puzzles. Could be useful for teaching someone how to play or just having a gauntlet of puzzles to play. I could see setting up a single player tournament that starts each round with a predefined (or randomized) puzzle situation. Win the match, and then you move onto the next puzzle until completion.

Here's an example of a puzzle: https://www.channelfireball.com/articles/puzzles-theyre-a-riot/

No files, tests, or entry points are named. First map how existing game modes and single-player tournaments are represented, then define the puzzle setup and progression flow; done means a player can complete predefined or randomized puzzle situations sequentially.

Written by the indexing model from the issue text.