Add progress bar for piece spawn, with colour change to red on last allowed spawn.
Moved resources into their own subfolder.
Conform to PEP8 standard.
Added a position->grid_cell function to the board, a representation of this grid, and collision detection when adding a piece to the board. Next up, returning pieces to the available set when they can't be added (or that player losing the game if now full), and edge matching to confirm/deny placement. Then rotation...