Even more impressive. Large to small is exactly the right way to do it. You seem to have thought through the problem for a bit before embarking on it, almost every choice you made is optimal or near optimal to get this done in an acceptable time.

It's interesting how much you learn about how our minds work by doing a job like this. All kinds of insights into color discrimination, shape recognition and so on, as well as how much of a job gets pushed down to our subconscious once we've done enough of it.