Smoke Effect Animation Test

I have decided to try the smoke effect on Adobe Flash. This is the scene when the kid is waiting in the Nurse room. He then looks out the window and sees her getting on the bus. The bus then drives away leaving a smoke trail. I did some research on tutorials on YouTube showing different ways to create a smoke effect. This is my first attempt of the smoke effect coming from the bus, it is rather simple however I do like how I've made the smoke so it follows the bus when it drives away and leaving the trail of smoke.

As this is my first attempt, improvements are still need to be made so for my next test I will change the smoke colour so it will be a dark grey as well as changing the size or the style of the smoke and my research will be developed during these test.