If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
Use the mouse to move the on-screen pointer. Press and hold the left mouse button to draw circles. Draw enclosed circles around groups of matching planets. Collect crystals from the comets and from the matching planets. Large matches of 4 or more will reward a higher multiplier. A mismatch of different planets will create a black hole, Destroy the black hole by drawing a circle around it.
Use mouse and drag to draw circles.