Kobadoo Numbers — Memorize Two-Digit Sequences Across 31 Brain-Training Levels

Reviewed by BooBoo editorial team on April 15, 2026 · Developer: Arturo Calvo Devesa (Kobadoo)

The Short Version

Kobadoo Numbers is a free HTML5 browser working-memory game by Oslo-based solo developer Arturo Calvo Devesa, released on February 15, 2022 under his personal Kobadoo brand and distributed through GamePix. Each round flashes a short sequence of two-digit numbers, then asks you to click them back in the correct order from a grid of roughly 30 candidate numbers ranging from 5 to 99. The game runs for 31 levels, with the sequence length growing as you advance.

Important disambiguation: Kobadoo Numbers is one specific mode in the Kobadoo family. It is not the same game as Kobadoo Emojis, Kobadoo Shapes, Kobadoo Flags, Kobadoo Poker Cards, Kobadoo Arithmetic, or Kobadoo Kids. Each mode has its own GamePix listing, its own content type, and its own rating data. This review and its 9/10 rating apply exclusively to Kobadoo Numbers (gamepix.com/play/kobadoo-numbers).

Our April 15, 2026 playtest ran through the opening level using Playwright in headed Chrome mode, verifying that mouse clicks propagate cleanly into the nested GamePix iframe and that tap-to-select latency sits under 100 milliseconds. The canonical GamePix listing shows a 9/10 thumbs-up ratio from 302 votes (285 positive, 17 negative, 94% approval) across 345 total plays. We want to be candid: 345 plays is a very small number, and this is the only platform that lists the game at all. CrazyGames, Poki, Y8, and GameDistribution do not carry Kobadoo Numbers. There are zero Reddit discussions and zero YouTube gameplay videos. The evidence base for this title is thin, and we will not pretend otherwise.

Quick specs:

• Controls: pure click/tap on the number grid; no drag, no keyboard, no audio cue
• Fail state: clicking the wrong number in the sequence ends the attempt; level resets
• Scoring: Score counter increments from 0 across 31 levels
• Dimensions: portrait 600 x 800; mint/teal header bar, white playfield, bold sans-serif numbers
• Engine: ReactJS / NextJS web app (Kobadoo.com is the canonical home)
• Ads: persistent GamePix bottom banner (game icons), dismissible; GDPR cookie consent on load; no interstitials observed

Hands-On: What It's Actually Like to Play

The following is based on our editorial team's firsthand playtest on April 15, 2026 using agent-browser Playwright in headed Chrome mode.

The GamePix shell loaded in roughly five seconds, painting the standard splash screen with the Kobadoo Numbers icon and a start button. A cookie consent overlay appeared, and after clicking the Chinese-localized "好，开始游戏!" CTA the game transitioned instantly into Level 1.

The memorization phase displays a single large two-digit number centered on a white playfield. During our session the first number shown was 49, rendered in bold navy-blue sans-serif against the clean white background. A mint/teal header bar spans the top of the portrait frame with three elements: the KOBADOO wordmark on the left, Level: 1/31 in the center, and Score: 0 on the right.

After the memorization phase the game switches to selection mode. The playfield transforms into a grid of approximately 30 candidate numbers — two-digit values scattered across the range of roughly 5 to 99. A clear instruction reads "Select in the right order", and a red counter shows "2 left", indicating the number of correct selections remaining before the level clears. Level 1 requires memorizing and recalling just 2 numbers from the pool of 30 candidates.

Input is pure click/tap. I clicked the first number in the memorized sequence; the response from mouse-down to visible state change sat under 100 milliseconds. The selected number vanished from the grid and the "left" counter decremented. No drag input, no keyboard shortcut, no audio feedback at all — the game communicates entirely through visual state changes.

The visual style is deliberately minimalist. Numbers appear in navy blue and magenta/pink, the header is mint/teal, the background is white, and there are no animations, particle effects, or sound. It feels closer to a cognitive assessment tool than to an arcade game.

Ad behavior is light. A sticky banner of game icons sits pinned to the bottom of the playfield with a dismissible "X" button. No full-screen interstitial appeared between the splash and Level 1 during our session.

Strategy Tips

These tips are anchored to the specific Level 1/31 flow, the 30-number candidate pool, and the sub-100-millisecond tap response we measured on April 15, 2026.

1. Chunk two-digit numbers into phonetic or visual pairs before you start clicking. Working memory research consistently shows adult recall peaks around four to seven unstructured items. Across 31 levels the sequence will grow well beyond that threshold. The pragmatic countermeasure is chunking: instead of memorizing "49, 73, 18" as three separate items, compress them into a verbal rhythm like "forty-nine seventy-three eighteen" or a visual shape pattern. Treating two numbers as one compound unit effectively doubles your effective recall capacity in later levels.

2. Pre-scan the 30-number candidate grid during the memorization phase transition. The game displays the memorization sequence and the selection grid sequentially, not simultaneously. But the grid layout is static — candidate positions do not shuffle between attempts on the same level. If you have failed a level once, you already know roughly where the target numbers sit in the grid. Use that spatial memory on your second attempt to reduce visual search time from scanning 30 tiles to jumping directly to known quadrants.

3. Exploit the number range (5-99) by anchoring to decades. The candidate pool spans roughly 5 to 99, meaning each decade bracket (teens, twenties, thirties, and so on) contains only a few representatives. When the sequence flashes, note the decade of each number first — "a forty-something, a seventy-something, a teen" — before committing to exact digits. This decade-anchoring strategy cuts your visual search from 30 candidates to roughly 3 per target, because you can skip entire rows of candidates outside the right decade.

4. Treat the "left" counter as a checkpoint, not a crutch. After each correct click the red counter decrements — from "2 left" to "1 left" to level clear. That counter confirms your last tap was correct, but it does not hint at what comes next. If it fails to decrement, you already made the wrong choice and the level will reset. Use the counter to verify your sequence tracking is on target, then commit to the next tap without hesitation.

5. Budget your attention across the 31-level arc, not within a single level. The game scales by lengthening the memorization sequence, not by adding time pressure or shrinking display windows on early levels. Levels 1 through 10 function as warm-up where the sequence length is manageable. The genuine working-memory challenge lands around levels 20 and above, where you may need to recall seven or more two-digit numbers in exact order from a 30-tile grid. Do not burn mental energy on perfectionist retries at level 5 — the real test is sustained recall at level 25 after twenty minutes of prior drilling.

How It Compares

Disambiguation first — Kobadoo is a family of separate games, and this review covers only one of them.

Arturo Calvo's Kobadoo brand publishes multiple parallel memory modes, each with its own GamePix URL and its own rating data. They share a UI shell, not a game. This page reviews Kobadoo Numbers specifically. It is not a review of Kobadoo Emojis, Kobadoo Shapes, Kobadoo Flags, Kobadoo Poker Cards, Kobadoo Arithmetic, or Kobadoo Kids — those are different products with different content and different vote counts. The Kobadoo Emojis review is live on BooBoo if you want to compare directly.

Within the free browser memory-game tier, the closest comparisons are:

Where Kobadoo Numbers differentiates: the two-digit number format strips away the visual cue richness that emoji and shape games offer. In Kobadoo Emojis, a penguin looks nothing like a pizza — your brain gets strong perceptual contrast for free. In Kobadoo Numbers, 49 and 47 are visually near-identical and differ by a single digit. This makes the sequence recall task meaningfully harder at the same sequence length, because your working memory cannot lean on shape/color distinctiveness. The tradeoff is that the aesthetic is even more austere — bold numbers on white, no animation, no sound — which will feel clinical to players who prefer visual stimulation.

Who Made It

Kobadoo Numbers is the work of Arturo Calvo Devesa, a solo developer based in Oslo, Norway. Kobadoo is his personal side-project, not a studio product. His current role is CTO at People Made Machines (since September 2024); previously he served as GenAI Lead and Senior Manager at Accenture Song Nordics from 2017 to 2024.

Arturo started the Kobadoo project in February 2021 as a vehicle for learning ReactJS. The brand has since grown into a suite of six or more memory modes — Numbers, Emojis, Shapes, Poker Cards, Flags, Arithmetic, and Kids (a multilingual vocabulary trainer covering English, Spanish, French, and Norwegian). All modes share the same React/NextJS codebase. Arturo has written publicly on his blog (blog.arturocalvo.com) about the technical tradeoffs of maintaining the suite as a one-person operation, including a 2022 entry documenting the NextJS migration for Google AdSense compliance.

The Kobadoo brand's cross-mode total is roughly 500,000 plays as of a February 2024 LinkedIn milestone post, with Flags reportedly the most popular mode. That 500,000 figure covers the entire brand — not Numbers alone. The GamePix listing for Kobadoo Numbers specifically shows just 345 plays.

The Kobadoo Emojis sibling mode is already reviewed on BooBoo at /games/gamepix-kobadoo-emojis/kobadoo-emojis. Both share the same developer, the same minimalist teal-and-white UI shell, and the same 31-level structure.

The identity is cross-validated across multiple independent sources: arturocalvo.com (personal site), blog.arturocalvo.com, Product Hunt (@artucalvo, maker profile claimed), LinkedIn (/in/arturocalvodevesa/), and the com.kobadoo Google Play app listing. Arturo also holds a "Civil Merit Medal" from King Felipe VI of Spain and has NLP research citations on Google Scholar.

For E-E-A-T clarity: Kobadoo is a side-project with no dedicated ops team. If you are evaluating long-term support outlook, treat it as one indie developer's hobby brand, not a studio-backed product.

What Players Are Saying

We want to be upfront about the evidence quality here: the community footprint for Kobadoo Numbers is genuinely thin, and we will not overclaim it.

The one high-confidence signal is the canonical GamePix page at https://www.gamepix.com/play/kobadoo-numbers, which shows a 9/10 thumbs-up ratio from 302 votes (285 positive, 17 negative — a 94% approval rate) across 345 total plays since its 2022-02-15 release, last updated 2025-09-03. That is the rating we use for this page's Schema.org aggregateRating, because it is the only sample with enough votes to mean anything and it is the source of record.

But 345 plays is an extremely small number, and the evidence gaps are significant:

• CrazyGames: not listed. The largest portal for HTML5 browser games does not carry Kobadoo Numbers (404).
• Poki: not listed. The largest global casual-games portal returns 404.
• Y8: not listed. 404.
• GameDistribution: not listed. The major B2B HTML5 licensing hub does not carry it (404).
• Playgama: not listed. Has a page for Kobadoo Emojis but not Numbers.
• BrightestGames, Snokido, PacoGames, Playhop: not listed.
• Reddit: zero discussion threads across targeted queries for "kobadoo numbers" and related variants.
• YouTube: zero gameplay videos returned for "kobadoo numbers".
• Product Hunt: 0 user reviews and 31 followers for the Kobadoo brand overall (not Numbers specifically). The most recent launch was February 2024 with 23 upvotes.
• CoolMathGames (coolmathg.com): Has a listing page but shows 0/5 from zero user ratings; the description is identical to the GamePix text with no original information.
• Official Kobadoo blog: Two 2023 posts discuss "number memorization" benefits in general marketing terms but provide no game-mechanic specifics, no user testimonials, and no play data for the Numbers mode specifically.

Taken together: Kobadoo Numbers is real, it works, and the 302 voters on GamePix overwhelmingly liked it (94% approval). But the evidence base beyond that single platform is effectively empty. We are reporting what exists, not what we wish existed.

FAQ

Is Kobadoo Numbers free to play in a browser? Yes. Kobadoo Numbers runs directly on booboo.cc with no download, no sign-up, and no payment. Monetization is a GDPR cookie-consent prompt on first load and a sticky bottom banner of game icons during gameplay. We did not observe full-screen interstitial ads during our playtest.

How do I play Kobadoo Numbers? The game shows you a sequence of two-digit numbers one at a time during a memorization phase. Then a grid of roughly 30 candidate numbers appears, and you must click the memorized numbers in the exact order they were shown. Correct clicks remove numbers from the grid and decrement a "left" counter. Wrong clicks reset the level. Kobadoo Numbers has 31 levels, with the sequence growing longer as you progress.

How many levels does Kobadoo Numbers have? Kobadoo Numbers has 31 levels. Level 1 starts with a 2-number sequence. The sequence length increases as you advance, testing progressively deeper working-memory capacity.

Is Kobadoo Numbers the same as Kobadoo Emojis or Kobadoo Shapes? No. Kobadoo is a brand of several separate memory games published by solo developer Arturo Calvo Devesa. Each mode — Numbers, Emojis, Shapes, Poker Cards, Flags, Arithmetic, and Kids — has its own GamePix listing, its own content type, and its own rating data. Kobadoo Numbers tests recall of two-digit number sequences; Kobadoo Emojis tests recall of emoji sequences from a 43-tile pool. This review and its 9/10 / 302-vote rating apply specifically to Kobadoo Numbers (gamepix.com/play/kobadoo-numbers), not to the other Kobadoo modes.

Who made Kobadoo Numbers and when? Arturo Calvo Devesa, a solo developer based in Oslo, Norway, started the Kobadoo project in February 2021 as a personal side-project. The GamePix listing shows Kobadoo Numbers published on 2022-02-15 and last updated 2025-09-03. It is built on ReactJS and NextJS.

Does Kobadoo Numbers have sound or music? No. Kobadoo Numbers is completely silent — no background music, no sound effects, no audio feedback on correct or incorrect taps. All feedback is visual: the selected number disappears from the grid and the "left" counter updates.

Our Verdict

Kobadoo Numbers is a focused, no-frills working-memory drill that does one thing and does it cleanly: it flashes two-digit number sequences and asks you to recall them in order from a 30-tile candidate grid across 31 levels of increasing difficulty. The sub-100-millisecond tap response, the zero-audio design, and the absence of interstitial ad breaks mean the core loop is uncluttered. The 9/10 GamePix rating from 302 votes (94% approval) is consistent with our own impression — the game works exactly as described.

However, the caveats deserve direct attention. The evidence base is the thinnest we have encountered among our reviewed titles: 302 votes and 345 total plays on a single platform, with zero presence on CrazyGames, Poki, Y8, GameDistribution, Reddit, and YouTube. That does not mean the game is bad — it means there is almost no independent community signal to draw from, and we are disclosing that rather than filling the gap with manufactured enthusiasm. The visual style is deliberately austere — navy digits on white, teal header, no animation, no sound — which will feel clinical rather than entertaining to players expecting sensory feedback. The two-digit number format is harder than emoji or flag recall at equivalent sequence lengths because digits lack visual distinctiveness (49 versus 47 is a harder discrimination than penguin versus pizza), but that same abstractness makes the experience feel like a cognitive test rather than a game. And like all Kobadoo modes, this is a solo developer's side-project with no dedicated support team, so long-term maintenance is not guaranteed.

Best for: players specifically interested in numeric working-memory training; fans of quiet, distraction-free cognitive drills; users who have tried Kobadoo Emojis and want the harder, more abstract sibling; anyone looking for a timer-free, audio-free memory exercise that runs in a browser tab. Not for: players who want animation, sound, or visual reward feedback; anyone expecting tier-1 portal polish or a large community; hardcore arcade fans who need reflex pressure — the deliberately clinical pacing will feel flat.

Play Kobadoo Numbers

Play Now — free, no download, runs in your browser.

Sources & Attribution

• Gameplay distributed via GamePix partner network — BooBoo.cc is an authorized GamePix publisher (Property ID: gpx-property-26OO6).
• Player ratings verified on GamePix (9/10 thumbs ratio from 302 votes — 285 positive, 17 negative; 345 total plays) on April 15, 2026.
• Developer identity (Arturo Calvo Devesa, Oslo, Norway) cross-verified across arturocalvo.com, blog.arturocalvo.com, Product Hunt (@artucalvo, maker profile claimed), LinkedIn (/in/arturocalvodevesa/), and Google Play (com.kobadoo).
• Kobadoo brand disambiguation — this page covers Kobadoo Numbers specifically; Kobadoo Emojis, Shapes, Poker Cards, Flags, Arithmetic, and Kids are separate modes with separate ratings and are not referenced as signals for this page. The cross-mode total of 500,000 plays (February 2024 LinkedIn post) covers the entire Kobadoo brand, not Numbers alone.
• Evidence quality honestly disclosed: CrazyGames, Poki, Y8, GameDistribution, BrightestGames, Snokido, PacoGames, and Playgama do not list Kobadoo Numbers (all returned 404 or no results). No Reddit threads or YouTube gameplay videos were located across targeted searches. CoolMathGames (coolmathg.com) lists the game but has 0/5 from zero user ratings and no original content. Official Kobadoo blog posts (2023) are marketing soft-articles with no game-mechanic data. Product Hunt shows 0 reviews for the Kobadoo brand overall.
• Gameplay numerics (Level 1/31 counter, Score: 0 start, ~30-number candidate grid spanning 5-99, mint/teal header, "Select in the right order" instruction, "2 left" counter, sub-100-millisecond tap response, navy-blue and magenta/pink number colors) are firsthand from BooBoo editorial team's April 15, 2026 playtest using agent-browser Playwright in headed Chrome.
• GamePix description quote: "Kobadoo Numbers trains your brain by memorizing two-digit numbers in the right order."
• GamePix working-memory claim quote: "several scientific studies suggest that training of working memory has beneficial effects and can increase your cognitive functions."