Add show_grid method
basic chess game
Refactor Piece code
Create README.md
Reformat offsets
Add placeholder methods
Add offsets for sliding movements
Change move to superclass
Add valid_moves method
Add stub for duplication
Fix typo
Add move function
Add pawn's possible moves
Add valid_moves and valid_move?
Add moves
Add moves
Add basic play method
Add game over logic
Fix pawn movement