This page contains spoilers from the 2-Tone Game. If you haven't already played the game, you might want to do so before continuing reading this page.
Rebus is a two-layered rebus puzzle.
The first draft is reminiscent of the final, but many little things changed:
Rebus
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
The basic contents of this puzzle stayed mostly-the-same, but many red herrings were shaken out by changing around the presentation.
The background behind the 26-square "key" grid started as light gray, but was green in the final. It looked pretty good gray. Unfortunately, players' iPhones (and perhaps other devices would have done the same thing) showed that light gray as black—after all, high-contrast colors are better for making things visible on small screens viewed outside. Unfortunately, this meant that the 26-square key grid looked more like some weird 21-square arrowhead. Thus, the un-thematic green background in the final.
The answer grid was at the bottom, under the rebuses. By the final, I'd moved it under the "key" grid. Thus, I hoped that players would look at the "key" grid as they looked at the answer grid, and figure out that they had to apply one to the other.
The first-version answer grid had 18 rows, the smallest grid that gave me a legible picture. But 18 is divisible by 2, by 3... Players looking at a 6x18 grid convinced themselves (reasonably) oh, it must be Braille. So the final version of the puzzle had a 19th row (and thus a 19th rebus) to steer players away from that blind alley.
That finch is from one of Darwin's drawings.