Stage 8 of GEOMGBITS — the capstone: seven trials in catching a wrong answer without working out the right one. Wrong units, impossible lengths, a hypotenuse that is not the longest, an area that beats its box, angles that refuse to close. Check first; trust the arithmetic second.
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 reject a wrong answer on sight — by its units, by whether the shape could exist at all, by the box that bounds it, or by corners that fail to add up. That completes GEOMGBITS: angle laws all the way to catching the errors, every step leveraged rather than laboured.