This is a Greek Squares puzzle being solved. To return to the Greek Squares page, click on the "End Animation" button. The animation will loop repeatedly, so don't worry if you miss something the first time through (or the 6th time...)

This animation will use yellow boxes to highlight the row, column or tile of the puzzle that it is currently working with, and to highlight the number that is being removed or enlarged. Most of the time, it will be showing the puzzle in "show only one number" mode (where all other numbers are hidden), so that you can more easily see the deductions.