If you just used pictures of 1s and 10s then it should work reasonably. Of course, the bot would then be right 50% of the time, so you'd need to include, say, t

If you just used pictures of 1s and 10s then it should work reasonably. Of course, the bot would then be right 50% of the time, so you'd need to include, say, ten pictures to rate to get the false positive rate down to one in 1024. This is, of course, starting to look like more trouble for the user than it's worth.