Destroy all particles for the king! Hover over a particle and you'll see white X's appear; these X's show which particles will be destroyed in the grid. Click on the particle to destroy it and everything nearby. Don't blast the king off the grid!

Look at the lines on the particles - that will show you how many particles will be destroyed. A green particle will remove the two spaces it's pointing to, blue particles will destroy a whole column, red particles will destroy every particle next to it, and yellow particles don't destroy anything; they only move one space in the direction the arrow is facing.

If you get stuck, click on the King to restart the level.