code: function(step){
      var styles = {}, 
        param = step.param,
        pairs = param.split(","), valid;
      pairs.forEach(function(pair){
        pair = pair.trim();
        if(pair){
          var tmp = pair.split( rSpace ),
            name = tmp.shift(),
            value = tmp.join(" ");
  
          if( !name || !value ) throw Error("invalid style in command: style");
          styles[name] = value;
          valid = true;
        }
      })
  
      return function(done){
        if(valid){
          animate.startStyleAnimate(step.element, styles, done);
        }else{
          done();
        }
      }
    }
docs: style: left {10}px,