The first of the hotspots, is the one above the cage. When clicking on the hotspot, this code runs:
switch (tdl) {
case 2:
tdl = 3;
break;
default:
tdl = 0;
break;
}
Unfortunately, all the other hotspots set tdl to 0, so the variable can never truly be set here.
Now for the Cho hotspots. It seems it was intended to have you click the hotspots in a specific order after tdl is set to 3 (from the above code segment). I have labeled them in the correct order here:
The hotspots labeled 1-6 will increase tdl by one if pressed in the right order. When you press the last hotspot, this segment of code is run:
switch (tdl) {
case 9:
araw = 4;
break;
}
tdl = 0;
araw is the variable used for the main Riven easter egg variable! aova is the other one. araw is normally set to 4 when you click the hotspot above the elevator on Garden Island:
So, it seems that this content was cut and replaced by the elevator hotspot. Or it could be that they changed the whole easter egg structure after having this initial "Cho code" in there.
(NOTE: The green/red rectangles are part of the hotspot debugging mode I added to the engine in ScummVM. Green = enabled, red = disabled)
EDIT: Well, turns out there's another piece of the puzzle. Clicking on the jammed lever outside of the cage in the beginning runs this code:
switch (tdl) {
case 1:
tdl = 2;
break;
default:
tdl = 0;
break;
}
Maybe there's a place where tdl is set to 1? The mystery continues!