How to increase total simultaneous keypresses?
You can use an array to hold key states
var keyStates = [ ];document.addEventListener('keydown', function(e) { keyStates.push( e.keyCode );}, false);document.addEventListener('keyup', function(e) { var pos = null; if( (pos = keyStates.indexOf( e.keyCode )) > -1 ) keyStates.splice( pos, 1 );}, false);