function createSound(name, url) {
  var deferred = Q.defer();
  soundManager.createSound({
    id: name,
    url: url,
    autoLoad: true,
    onload: function() {
      deferred.resolve(this);
    }
  });
  return deferred.promise;
}

function sign(x) { return x > 0 ? 1 : x < 0 ? -1 : 0; }

function lerp(from, to, p) {
  return to * p + from * (1 - p);
}

function ease(v) { return v * v * (3 - 2 * v); }

function easeOutExpo(t, b, c, d) {
  return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
}

function color(r,g,b,a) {
  return 'rgba('+r+','+g+','+b+','+a.toFixed(5)+')';
}