Double click on the applet to bring focus to the applet.
Use arrow keys to move the light gray box.
Using light gray box, move blocks so that they disappear.
Rules for disapperring box:
* When green boxes touch each other, the color of the boxes becomes yellow
* When yellow boxes touch each other, the color of the boxes becomes red
* When red boxes touch each other, they disapper
If it is not easy to navigate using keys, change the view point by dragging the scroll bars
shown at the upper right corner to the point where it is easier to navigate