That doesn't look at all impressive. It seems easy to write a solver for it. Especially considering most spam bots are quite happy with relatively low rates of succeeding, they can just brute-force until they find one they can solve.
on one scenario you 'll select a 24x24 square out of a 200x100 pixel picture, the success rate is 2.8%
50x traffic is too obvious to ban :)
I am the developer of clickcha. Appreciate the input, but you seem to be forgetting that bruteforcing can be avoided by temporarily banning the IP for some time after certain number of incorrect attempts.