Sudoku Touch · 3 min read

Ten number buttons took too much of the screen. Writing the number anywhere became the input for six more apps

A large blue handwritten 7 drawn across a Sudoku board on an iPad

Sudoku Touch was built at Shiny Things to test a handwriting recognition engine in a real game.

RoleDesigner, working with a developer and the founder

Timeline2011–2012

ProductSudoku Touch for iPad, then iPhone

CompanyShiny Things

Problem

Shiny Things had built a handwriting recognition engine and needed to know whether people would use it. Sudoku is nothing but digits, so it was a good test. Ten number buttons take a lot of room, and on the iPhone’s 3.5" screen each one is tiny. In time-trial mode a wrong tap costs a penalty.

Solution

I designed an input where you write the number anywhere on the screen, as large as you like. With no input pad, the whole screen goes to the board.

Constraint

Bigger buttons meant a smaller board

Apple recommends 44 point touch targets. Ten of them take over the screen, and making room for them shrinks the board. The squares were already under 44 points, but a missed square is easy to fix and isn’t penalised. A wrong digit is, so input was the part that needed the room.

Concepts

Four ways to enter a number

Touch screens were new, and button pads still shaped my first ideas. Handwriting recognition was immature, but needing only a few characters kept misreads down.

A sketch of an iPad in landscape with a Sudoku grid and a small box on the right labelled draw number here — **Pad beside the board:** favoured right-handers, and a left-handed mode went against keeping it simple.

A sketch of a portrait Sudoku board with a drawing area underneath, plus notes on selecting, noting and clearing a square — **Pad below the board:** suited either hand, but a player racing the clock would brush the board and enter numbers by accident.

Two iPad wireframes of a Sudoku board with numbers, notes and clear buttons and a grey drawing area, one with the controls above the area and one beside it — **Wireframes for the pad below the board:** I took this concept as far as wireframes before dropping it.

A sketch of a Sudoku grid with one square selected and a note to draw the number over the grid — **Write on the square:** direct manipulation, but even on an iPad the squares were too small to write in.

A sketch of the final concept: a full-screen Sudoku board with the note draw anywhere to enter your answer — **Write anywhere:** obvious in hindsight, and the one I took forward.

Gestures

Writing had to share the screen with every other touch

I mapped every gesture so none clashed, and built click-through prototypes in Keynote to test how to enter and clear numbers and notes.

An open sketchbook with storyboards for clearing a cell with a clear button, clearing notes with a zoom gesture, and confirming a handwritten digit with OK or redraw — **Explorations:** clearing numbers and notes, and confirming what the engine read.

Final flows

One gesture to enter, a few taps for the rest

Tap to select a square, write to enter a number, and write again to replace it. A two-finger swipe clears it. Double-tap switches to notes, which use the same gestures. Beyond writing, the game needed only taps and one swipe, so the interface stayed minimal.

A prototype frame of an iPad Sudoku board with a large blue handwritten 7 drawn across it — **Entering a number**

A prototype frame with a large blue handwritten 9 drawn across the board over a selected square — **Replacing a number**

A prototype frame with a large blue handwritten 5 drawn across the board and a grey square marking another selection — **Entering a note**

Numbers being entered in a Sudoku Touch game

Outcome

The input design outlived the game

Sudoku Touch launched in May 2012 and is no longer available, but its input design was used in all of Shiny Things’ maths apps. In Quick Maths, speed runs became a challenge in their own right (watch a speed run).

Testing was informal, so I can’t put a number on how much more reliable writing is than tapping. I’d run the same time trial against a button pad and compare errors.

6 more apps

Quick Maths, Quick Maths Plus, Quick Maths Jr, Quick Clocks, Quick Fractions and Shape Lab reused the input design

Under 10 seconds

Some Quick Maths players finished ten arithmetic questions in under ten seconds. My best was about twelve

In testing with friends and family, children and adults learned to play quickly and found writing numbers easy

All projects Simon SeeberYou’ve seen how writing anywhere on screen replaced a row of tiny buttons, now see more of my work