How to play: Blue uses the "W" and "S" keys to move up and down. Red uses the "up and down arrows" to move up and down. Rule: For fair play, both players must not 'press and hold' their keys to move as it will disable the opponent's ability to move. Press your keys repeatedly instead. (This problem I believe is impossible to solve when using mBlock as it is impossible to press and hold two keys at the same time to execute 2 scripts simultaneously in mBlock.)