If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Move your mouse to stock crystals of the same color into a tower. Click the mouse button to create a tower fusion. The more crystals you stack at one time, the more points you'll get from the tower fusion. Don't let your tower run into crystals of a different color, or your tower will get blown apart!
Use mouse to interact.