Puzzle 23 - Squarely Squaring Squared Squares

Puzzle:

“Four square meals a day is what you need to get started,” is all your doctor cryptically advised. Whatever, back to these letters—sorry, numbers—for the task at hand. Hey wait, though, they don't look quite right? The key to keeping things under control is a smile and speed, but after that there's a varying number of sides to every situation…

[Solution: The given numbers in the squares are meant to represent side lengths, but the original 13 and 5 aren’t correct; using alphanumeric (13,5 → m,e) & a four square cipher (clued by the title and flavortext) with keywords smile and speed, you can get the new numbers 3 and 2 (c,b → 3,2). Players can solve for all the side lengths of all the squares using algebra and assigning variables; this is a geometric problem known as squaring the square. Then, you find the side lengths of the colored squares, getting 10,21,4,1,19, which when converted to letters yields the answer JUDAS.]