CASI00 icon

CASI00

CASI00 is the old digital watch game. Start the stopwatch, stop it, and you win only if the hundredths read 00. It runs on a working F-91W lookalike with a backlight, a time mode, seventeen skins and keyboard shortcuts.

A black digital watch modelled on the Casio F-91W, branded CASI00 F-00W with ANARCHRONOGRAPH and REFUSE RR RESIST on its face, its stopwatch reading 00:00 00 under the heading STOP IT ON 00, IF YOU CAN.
Open CASI00

What problem does it solve?

None, which was the point. In high school, anyone with a digital watch had a game on their wrist. Start the stopwatch, stop it, and check the hundredths. Anything but 00 was a miss. CASI00 brings that game back on a watch that looks the part.

How it works

The watch behaves like the stopwatch on an F-91W. START·STOP starts and stops the count, starting again resumes it, and LIGHT resets it once it is stopped. Stop on 00 and the digits blink. MODE switches to a time mode with the day, date and current time, while the stopwatch keeps running in the background. The face swaps the original print for REFUSE, RR and RESIST, and ALARM CHRONOGRAPH becomes ANARCHRONOGRAPH. Seventeen skins recolour the case, the frame and the backlight, from classic black and gold to Game Boy, Breaking Bad and Cyberpunk 2077.

Whom it’s for

Anyone who wore a digital watch to school, and anyone who thinks a hundredth of a second is easy to catch.

Tech

A single static page with no build step and no backend. The watch is one inline SVG with seven-segment digits drawn as paths, timed with performance.now() so a press counts from the moment of contact. Set in Eurostile. Skins are CSS custom properties, and the last one you picked is kept in your browser.

Frequently asked questions

How do you play?

Press START·STOP to start the stopwatch and press it again to stop. You win if the hundredths read 00. Starting again picks up where you stopped, and LIGHT resets to zero.

Why is it so hard?

A hundredth of a second lasts 10 milliseconds, far shorter than anyone's reaction time. Every hit is part timing and part luck.

Was this a real game?

We played it in high school on our own watches, and we were not the only ones. People elsewhere remember playing the same game at school with a digital watch.

What do the buttons do?

START·STOP starts and stops. LIGHT lights the screen and resets when stopped. MODE switches between the stopwatch and the time, where START·STOP toggles 12- and 24-hour time.

Are there keyboard shortcuts?

Space for START·STOP, L for LIGHT, M for MODE and S to change the skin.

Does it work on a phone?

Yes. Tap the watch buttons, and swipe left or right to change the skin.