A Number Puzzle Designed to Sharpen Quick Thinking
A number puzzle that teaches maths without ever saying so.
Role
Lead UI/UX Designer
Focus
Retention Design, Multi-stakeholder Products
Level 10
Tap the multiples of 4 in ascending order
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3424785126027667294384651831945
ROLE
Lead UI/UX Designer
FOCUS
Retention Design, Multi-stakeholder Products
TIMELINE
6+ months
01The problem
Maths apps forgot the fun
Learning apps for maths keep about 12% of kids after a week. Puzzle games like Candy Crush keep 60 to 70%. The mechanics are the same. Kids drop the app that says “learning” and cannot put down the one that says “play”.
So how do you make a learning game as fun as a puzzle game? The goal we set: 70% of players back the day after they start.
Who did what. I was the lead designer on a team of four, and owned the design end to end, from the research to the screens.
Day 7 retention maths learning app versus casual puzzle game, out of 100%
Maths learning app12%
Casual puzzle game60–70%
Four weeks of asking
I like games that make me think, not just memorize. Like Chess, but for math.
A playerAge 12 · interview
24Interviews, an hour each
185Survey answers from kids, parents and teachers
15Apps taken apart, learning and puzzle
We took apart Khan Academy Kids, Prodigy and Monument Valley. The gap between learning apps and games was plain to see.
Four kinds of player
Kids, 8 to 12
Want rewards right away
Bored by long explanations.
Maths lovers
Want a real challenge
Want to share a clever solve.
Teachers
Need it to match the lesson
Want to track progress.
Casual gamers
Expect a polished game
Want short sessions.
The four rules every feature had to pass
Kids responded best to small goals they could reach straight away; big, distant goals lost them. That gave us a filter. Every feature had to pass all four rules.
Rule 1Fun first, maths hiddenA puzzle with no lessons and no maths words, where the maths happens on its own.
Rule 2Answer every action at onceSomething to see, hear and feel within half a second.
Rule 3No tutorialThe game teaches itself. You are playing within 30 seconds of opening it.
Rule 4Easy to start, hard to masterGood for a 5-minute go, deep enough to keep going for months.
02What was decided, and what it cost
Meet Numzy
A fast number puzzle. Each level sets one goal, such as “multiples of 4 in ascending order”. You tap the right numbers before the minute runs out. Kids build a feel for numbers without noticing they are learning.
Try the mechanic
Level1
01:00
Score00
Objective
Tap the multiples of 4 in ascending order
Decision 01
Decision 01: Tap to a goal, picked from five prototypes because it asks the least of you and still has depth.
We prototyped 5 mechanics, among them tap to match, drag and drop and gesture combos. Tapping to a goal won. It asks the least of a new player and still rewards strategy.
The board never sits still. It reshuffles after every tap, right or wrong. You cannot remember where a number was, so you read the board again each time.
Accuracy beats speed. Every right tap is worth the same. A wrong tap costs 8 points, so only a run with no wrong taps earns three stars.
Perfect run
Level10
00:01
Score76
You Won !
76 points
Every right number and no wrong taps is a perfect run: three stars, 76 points.
Three wrong taps
Level10
00:09
Score52
You Won !
52 points
Each wrong tap costs 8 points. Three of them cost a star too: 76 became 52.
Time's up
Level10
00:00
Score38
Time's up !
38 points
Time's up is always no stars. The points you made stay: two right taps, 38.
Decision 02
Decision 02: A square grid instead of the hex grid we loved.
18 students, ages 8 to 14, tested three versions.
Before, on the hex grid. 42% finished a level. Kids were confused about how tiles moved. “It feels random,” said a player, age 11. The board also grew with each difficulty, from 9 tiles to 12, 15 and 18, so the tiles shrank and the numbers got hard to read. Tiles of one colour were kept apart, and a row of one colour was hard to tap.
After, on the square grid. 90% finished. The pattern was familiar. “Oh, I get it!” said a first-time player.
Levels finished 18 students, three versions
Hex grid42%
Square grid90%
The first wireframesA grey three by three
Everything grey, with power-ups under the board. The tile colours did not stand out against the grey.
The first testA hex board
What changed: nine hex tiles in three columns, the timer in a hexagon. 42% of the students finished a level.
The second testA square board
What changed: square tiles in rows and columns, the timer in a pill. The board grew with difficulty, here four by four. 90% finished.
What shippedThe level screen
What changed: the level and score on panels beside the timer, which keeps the only heavy outline.
The board in four stages, drawn from the original wireframes and screens. The two tests are the playtests with 18 students.
Bigger was not harder. The square board grew with difficulty too, from 9 tiles to 16. Hard goals still finished fast, because the board ran out of tiles. A level had no steady length: a player could take 30 seconds on an easy level and 10 on a hard one. The numbers climbed to three digits, and sometimes four. Balancing the goal, the board and the numbers took several reworks of the engine and the difficulty curve.
34247851260276672
9 tiles Two-digit numbers.
34247851260276672943846
12 tiles Still two digits.
582586587576589584581588585590583580579578577591
16 tiles Three digits, sometimes four.
The same board at three sizes. The hard board is the one from a hard level of the second test.
Decision 03
Decision 03: No tutorial, difficulty that climbs with the level, and the animation budget spent on feedback.
The old tutorial took up the whole of level 1, nudging players to click through everything before they could play. For a game this simple, that was too much. Now each level opens with its goal in one sentence, and that is the teaching. Difficulty climbs level by level. We cut screen transitions and spent the time on what a tap does to a tile.
Level10
01:00
Score00
Level 10
Objective
Click on multiples of 4 in Ascending Order in 60 sec
The goal in one sentence, with the words that matter in bold. It is all the teaching a level needs.
Start begins the clock. Nothing moves until you are ready.
During play only the timer and the board carry an ink outline. Everything else steps back.
Playing
Level10
00:55
Score00
Only the timer and the board get an ink outline. Level and score sit on quiet panels.
Last 10 seconds
Level10
00:09
Score00
The last 10 seconds turn the timer ink, with white digits. Colour only, no motion.
I took the colours through three rounds. The first screens were all grey, and the tile colours did not stand out against it. The first test used bold, bright tiles. The second test’s purple palette confused players, with white numbers on pastel tiles. In testing, patterns inside the tiles distracted players, and some found the colours too bright. What shipped is calmer: flat tiles and ink numbers.
The first test White numbers on bright tiles
58Blue #1F9EF12.9Fails
58Green #12D0822.0Fails
58Yellow #FCBA021.7Fails
58Red #F72F3B3.9AA
The second test White numbers on pastel tiles
58Pink #F498CF2.1Fails
58Cyan #8CE5FB1.4Fails
58Green #A6F0711.4Fails
58Lilac #C5A6FF2.0Fails
What shipped Ink numbers on calmer tiles
58Pink #F4A4D110.2AAA
58Cyan #79E1FA12.8AAA
58Green #97ED5513.4AAA
58Yellow #FEE15A14.8AAA
1AA 321
WCAG contrast of a tile number against its tile, on a scale of 1 to 21. Tile numbers are large text, so AA needs 3:1 and AAA 4.5:1. The test colours are sampled from the test screens.
Every colour has one job. The tile colours mean nothing, so no one has to learn them.
Start
Action#6760FE
Anything you tap: buttons, level tiles, arrows, switches.
76 points
Reward#FFB31F
Stars and points, nothing else.
34
Wrong#FF6F82
The flash on a wrong tap. Only on a tile.
00:09
Ink#0D0C20
Text, outlines, the ring on a held tile, the last 10 seconds.
Tiles4 colours
Board tiles only. They are decoration and carry no meaning.
Decision 04
Decision 04: Numzy Kids: no timer, no leaderboard, for ages 5 to 8.
Numzy was built for students and anyone who likes numbers and puzzles. Numzy Kids is only for young children, ages 5 to 8. It has no timer and no leaderboard, so children build a feel for numbers without the pressure. Each level is a short set of questions, one sum at a time.
The question
Question 2 of 5
Pick the right answer
4 X 3 =___ ?
Question 2 of 5, with dots to match. A level is a short set of five, with no clock.
One sum at a time, answered on a 3 by 3 board.
Kids controls
Question 2 of 5
Pick the right answer
4 X 3 =___ ?
Home and sound only. With no timer, there is nothing to pause.
Numzy controls
Level10
00:55
Score00
Numzy's bar, for comparison: home, pause and sound.
1Read the objectiveEach level tells you which numbers to tap, and in what order.
2Tap the right onesCorrect taps score points, then the board reshuffles.
3Avoid wrong tapsWrong taps cost points. Only a perfect run scores highest.
4Beat the clockClear every right number before time runs out.
How to play, in four steps
Level10
00:47
Score19
Paused
Level 10 objective
Click on multiples of 4 in Ascending Order in 60 sec
Timer stopped at 00:47
Paused: the goal again, and the time it stopped at
Numzy Kids: its own home and logo
03What happened
After launch
1M+Downloads
74%Came back on day 1. The target was 70%.
38%Came back on day 7. Three times the average for learning apps.
4.7★Average rating, from Play Store reviews and our player communities
Day 7 retention where Numzy landed, out of 100%
Maths learning app12%
Numzy38%
Casual puzzle game60–70%
My kid plays for hours without realizing he’s practicing math!
A parentBeta testing
What players told us, and how we prioritised
Most of the raw research is lost to time. These are the playtest notes and player reviews that survived, grouped by theme.
Affinity map
Playtest notes and player reviews, clustered into seven themes, each ending on what we did about it
💚What players loved
A simple, clean look
Clean gameplay, fun for puzzle lovers
Like Sudoku on a dad's old phone
Keptone goal, one board
🎨The look
All grey at first: the colours didn't stand out
The first purple palette confused players
Patterns inside the tiles distracted
Colours too bright to be comfortable
Shippedcalmer colours, flat tiles, ink numbers
🌙Asked for
A theme switcher
Dark mode
In the pipelinedark mode
🧩The challenge
Hard goals, but the board emptied fast
Numbers grew to three digits, some four
Reworkedthe engine and the difficulty curve
⬡The hex board
Tiles shrank as the board grew: 9, 12, 15, 18
A row of one colour was hard to tap
Changedto a square grid
📦Running out
Some players finished 100 levels in a day
Released50 more levels, fast
🏆The leaderboard
Players raced for the top
…and got only their name for it
Carried into future productsrewards for everyone
We sorted what we heard by how much it hurt the game and how often it came up. The praise told us what not to break.
Prioritisation
The same feedback, sorted by how much it hurt the game and how often we heard it (from memory, not counts)
Hurts the gameNice to have
Fix nowHurts the game · heard more
Ran out of levels
Steep, uneven difficulty curve
Hard levels over faster than easy ones
Fix, even if quietHurts the game · heard less
Hex tiles shrank until numbers were hard to read
A row of one colour was hard to tap
Plan for laterNice to have · heard more
Dark mode
A theme switcher
Rewards beyond the leaderboard
Fix when it's cheapNice to have · heard less
Colours too bright
Patterns inside the tiles
Heard lessHeard more
ProtectWhat players loved: don't break it while fixing the rest
A simple, clean look
Clean gameplay
Like Sudoku on an old phone
What players said
I used to play Sudoku on my dad’s old phone. This game brought those memories back. It’s simple, easy to play and a good way to pass the time.
A playerReview
I really love the simple UI and the clean gameplay. I love puzzle games, and this one was fun to play.
A playerReview
I liked the overall feel of the game and its simple mechanics. Highly recommended if you like number puzzles.
A playerReview
Numzy was retired in February 2024.
04What I learned
Kids understood the familiar grid
The hex grid was the idea we were proudest of, and the one kids understood least. We spent that budget on animation instead. Numzy was the company’s first game, so most of this was new to all of us.
Carried forwardA leaderboard is not a rewardPlayers raced for the top, and all they got was their name there. The products I designed after Numzy give every player a reward with real value.
Next timePlan the runway100 levels felt like plenty. Some players finished them in a day. I’d plan how new levels arrive before launch, not after.
Next timeCount up, not downA 60-second countdown adds stress. I’d time each level instead and give stars for speed: under a set time earns three, slower earns two, and so on. It’s calmer for players, and easier for the engine to scale.