Crane and Turtle Problem Animation is a free, install-free learning tool that runs entirely in your browser. It turns the classic crane-and-turtle problem — two kinds of items with different per-unit values and counts — into an area diagram so the solution becomes something you can see. The setup panel lets you change the labels, values, counts, and units freely, so you can adapt it from counting legs to the total price of oranges and apples or the total value of coins.
Click the canvas to advance the slides, moving from the problem statement to the area diagram. The dimensions, split, orange frame, red deficit, difference, answer, and formula are separate layers you can show or hide independently with the action buttons, so you can walk through the reasoning one step at a time.