Tell the time the way your math teacher would have wanted.

Math Chalkboard is an analog watch face for Wear OS drawn like a classroom chalkboard: green slate, a brass rim, gold hands, and hand-written problems where the numbers should be. Solve the problem and you have the hour.

EVERY HOUR IS A PUZZLE
Each position on the dial is a different kind of math, with a little physics and chemistry thrown in:
- Hexadecimal and binary: 0xC, 1001₂
- Calculus: d/dx (8x) and the integral from 0 to 2 of 2x dx
- Factorials and permutations: 5!/4!, 4!!, ⁴P₂
- Logarithms and Euler's identity: log(10¹⁰), ln e, −e^(iπ)
- Floors, ceilings and absolute values: ⌊π⌋, ⌈e⌉, |−11|
- Number theory: lcm(2, 5), φ(15)
- Complex numbers: |3+4i|
- Science: the pH of pure water, Ohm's law, the atomic number of carbon
- Plus powers, roots and an equation to solve

CHOOSE YOUR PROBLEMS
Every hour has three problems to choose from, 36 in all. Open the watch face editor, swipe to an hour and turn the crown to pick the one you like. Mix easy and hard, or make the whole dial calculus.

Behind the dial, faint half-erased formulas fill the board: the quadratic formula, the distance formula, E=mc², PV=nRT and more.

USEFUL AT A GLANCE
- Battery percentage and step count, shown in chalk either side of the center
- Both are complication slots, so you can swap them for any data you prefer in the watch face editor
- Day and date, for example "Tue Sep 26"
- Sixty second markers and a second hand that ticks once a second

EASY ON THE BATTERY
- A dimmed always-on display on a black background
- Built with the Watch Face Format, so it runs efficiently and contains no code of its own

PHONE COMPANION APP
The phone app is optional and does not need to be installed for the watch face to work. It has:
- The working for every problem: tap any of the 36 to see why it equals its hour
- A quiz: which hour does it stand for?
- A step-by-step guide to installing the face and customizing the dial

REQUIREMENTS
- A Wear OS watch running Wear OS 4 or later
- Install from the Play Store on your phone by choosing your watch from the device list under the Install button, or search for Math Chalkboard in the Play Store on the watch. Then touch and hold your current watch face and choose Math Chalkboard.

Math Chalkboard collects no data and needs no permissions, on the watch or the phone.