step: function(key, fx) {
var value = fx.end;
key = regexpColor.test(value) ? 'fillColor' :
regexpGradient.test(value) ? 'fillGradient' : null;
if (key) {
StyleSheet.step(this, key, fx);
}
}
step: function(key, fx) {
StyleSheet.step(this, 'strokeColor', fx);
}