Good Eye: Guess the Size

How good is your eye, really?

A shape appears on screen. You name its size in inches or millimeters. No ruler, no grid, nothing to compare it against. After every guess the shape comes back at true scale with a ruler against it, so you see exactly how far off you were.

Every run ends with your score, and your best score waits on the home screen for you to beat.

WHERE THE IDEA COMES FROM

Nikola Tesla built his machines in his mind before he built them in metal, and could give the dimensions of every part.

"I needed no models, drawings or experiments. I could picture them all as real in my mind." — Nikola Tesla, My Inventions, 1919

Most of us can't do that. Almost nobody has ever tested how close they can get. Good Eye is that test.

HOW IT WORKS

• A shape appears
• You name its size in inches, down to 1/16, or in millimeters
• Close enough, you score and move toward the next level. Too far off, you lose one of three lives
• Every guess comes back at true scale, with a ruler and your error in percent
• The screen calibrates itself, so every inch on screen is a real inch. A credit card fine-tunes it if you like

WHY IT'S HARD

• No reference objects, no grid lines, no scale bar while you guess
• The margin of error tightens as you go, from ±15% down to ±2%
• Your eye has habits, and this game exposes them

FREE, AND PRO

Levels 1 to 3 and a new daily challenge every day are free. Good Eye Pro is a one-time purchase, no subscription:

• Levels 4 to 6, down to ±2%
• Training: no lives, pick your tolerance
• Rings and angles: guess ring sizes and angles by eye
• Stats: your progress, and the habits your eye has

BUILT FOR SHORT SESSIONS

A run takes a minute. Getting good takes a lot longer. Play one on the bus, one in line for coffee, one during the commercials.

WHO THIS IS FOR

Designers, engineers, makers, woodworkers, tailors, model builders, and anyone who has ever said "that's about an inch and a half" and wanted to know if they were right.

Plays in English, Spanish, Portuguese, German, French, Italian, Polish and Japanese.
No ads, no sign-up. Only your best score leaves your phone, for the Google Play Games leaderboard.

Tesla had a good eye. Now see how you do.

Recent changes:
• See how your eye compares: after every run and daily challenge, find out what percentage of players you beat
• Your daily streak on the home screen, and an evening reminder when today's challenge is still waiting
• Free levels no longer stop mid-run: after level 3 you play on
• Pro: Objects mode, 18 real things shown at true size