Illumine Game Recap 
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How the Clue Works
There was very little trickery in this puzzle  it's basically a surveying problem. Teams had to locate the three original circles from the page on the field and extrapolate the positions of the remaining 16.
One key piece of information was that the page and the field were both constructed to scale. A quarter inch on paper translated to ten feet on the field. The three circles on the page were each a quarter inch in diameter, were a quarter inch apart, and in a perfectly straight line. There were only three such circles on the field  in the far corner, with one of the circles wickedly hiding in some taller grass.
The other interesting aspect about the page was that the letters were distributed on a regular hex grid (optimal 2D circle packing). This reduced the problem to one of measuring in terms of grid units  10 foot increments, and angles of 60 degrees.
A few methods for locating the circles (can certainly be combined):
The Solution
The circled letters formed the answer when read from toptobottom, starting with the near (West) edge of the field.
The solution phrase, "Old Cannery Furniture", told the teams to head to the Old Cannery Furniture Warehouse in Sumner. One edge of the page also contained the sentence, "When you get there, ask for Linda at the front desk", to let the teams know what to do once they arrive.
Design Notes
The idea to do something with crop circles arose at on of the very first theme planning meetings when someone proposed an XFiles/UFObased Game. Luckily, UFOs fit quite well into the Illuminati universe.
The original planned scale was a bit more epic, since "real" crop circles tend to be significantly larger  a single circle might be half the length of the final field or more in diameter. Reality set in as clue design progressed and the circle diameters trended downward through 20 feet to their final size of 10.
We hoped to come up with a form of the puzzle that used the position/appearance of the component circles more directly. The fear was that such a design would change the location into a pure "aha" (or, "you see it, or you're screwed"). In Shinteki: Untamed, some of us encountered a surveying puzzle that required an extremely high degree of accuracy (an error of 6 inches over 200+ feet would be too much), which inspired the final form of this puzzle. The goal was to design a location that required some careful measurement (and maybe a bit of math), but not be overly frustrating when attempted with fairly crude equipment.
The unused letters on the page were random, but roughly followed the frequency distribution of English.
GC Notes
Setting up the field began before sunrise. Our shoes were soon soaked and our hands numb from the dew.
We had plotted the centers of the first ten circles when I (Derek) noticed we'd made an error in the first two; we'd have to either start over or knock down one of the neighboring fences to finish. This lovely moment exactly coincided with an incoming call from GC, which informed us that the first team was ready to visit the park and how long would we be? Since I was a bit frustrated, cold, wet, and running on roughly two hours of sleep at the time, I'm not sure how calmly my response came through.
Semirandom chance in placing the first circle caused the final one to be in the tall grass. The original idea was to have an entire cluster down there.
After two or three teams had gone through, we noticed someone unloading a riding mower down at the East end of the field. Visions of shards of chewedup plastic ruining the puzzle sent Jessica after the worker, asking whether he could wait a bit and let us pick up the one circle hiding in the tall grass. He told us not to bother  he'd just mow around that one. Thus, we wound up with a wellmanicured lawn across the entire field, except for one 10footdiameter circle of overgrown grass. And some teams still didn't notice the circle hidden within!
We anticipated that most teams would want to use the 3rd solving approach. The orange string was provided to assist here  teams could use some length of the string to construct an equilateral triangle (60 degree angles  woot!) with sides equal to the circle diameter. This master triangle would then allow the teams to see which circles aligned with the rest, and provide an easy means to measure distances.
Most teams had their own string/rope/measuring tapes  we were pleased to see that several teamowned ropes were at least orange.
We were a little worried about the accuracy of the field until the first team (Fuchsia, at this point) made it through. Also, major kudos to that team for putting their progress temporarily on hold to help find my laser pointer.
We had a few magnetic compasses onhand to loan to any teams that might want them. I think we only offered any to just one team, and no teams actually borrowed one. Several teams had their own, however.
