When Snake eats an apple, Tetris will suffer a hard-drop.
When Tetris cleans a line, Snake will grow a node.
Use KeyListener for all keystrokes from both players in a single JPanel. Key Binding can support two Jpanels in a JFrame to receive keystrokes individually. Yet I need KeyListender for a Swing.Timer to count time for stepwise operation of the game.
http://zetcode.com/tutorials/javagamestutorial/tetris/
https://github.com/janbodnar/Java-Tetris-Game
http://zetcode.com/tutorials/javagamestutorial/snake/
