Stage 6 of GEOMGBITS: seven trials in circles. Three approximations do nearly all of it — the circumference is three diameters plus about 5%, a circle fills just under ¾ of the square it sits in, and every arc and sector is simply a fraction named by its angle.
Each trial is locked until you clear the one before it. Every level scores out of 1000 — 600 for accuracy, 400 for speed — so speed alone can't clear the bar; you have to solve most problems, and quickly. Reach 650 to unlock the next.
You can size a circumference from a diameter and back again, get a circle’s area from either the square it sits in or its radius, and read any arc or sector straight off the fraction its angle names — all without reaching for π to ten places.