Circular Board

- [x] Drawing a circlular board using canavs
- [x] Displaying tiles
- [x] Declaring the underlying data for keeping track of planes on the board
- [x] Defining starting points for players
- [x] Defining where planes change layers

The issue lists circular-board work for drawing the board, displaying tiles, tracking planes, defining player starting points, and changing layers, but it names no files or tests. First inspect the current board implementation and confirm whether these checklist items are already complete; done means the listed board behavior works consistently.

Written by the indexing model from the issue text.