How to use flash to do the effect of water rising in the cup?

Very simple, it is actually a square animation process. Draw a blue rectangle in the first frame, then press F8 to change it to a graphic or movie clip, and then lower the transparency, alpha, in the property box to make it look like water. Press F6 to add a key frame in 15 frame (no matter which frame you are in), and pull up the rectangular deformation, indicating that the water has risen, then go back to the first frame and add the deformation action. Build another layer, add a water cup and put it under the water layer, and it will be OK.