Quick refactoring session. I extracted magic numbers like PLAYER_SIZE, GRID_RESOLUTION, and BACKGROUND_COLOR into a dedicated Constants.ts file so they’re easier to tweak and reuse across the codebase.

Also added a level migration system that automatically pads smaller levels with empty cells when the game grid size changes. This was needed because I bumped the grid width from 18 to 19 columns, and existing levels needed to gracefully handle the size difference without breaking.