Player 1 (Clu - The Yellow Character) uses WASD for steering and can press Q every two seconds to throw their disk. Player 2 (Tron - The Blue Character) uses IJKL for steering and can press O every two seconds to throw their disk.
If the trails from the last match are still visible when you begin the next round, press space again. Thanks to SaucissonSauvage for the original project TRON.