Pearl Diver HD vs Stack Up
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Pearl Diver HD
Dive into the ocean depths to master the number line, including fractions and decimals, by collecting pearls. This game is designed by educators to align with Common Core standards for grades 3-8.
- Number line mastery
- Fractions and decimals
- Common Core standards alignment
- Progress tracking
- Educational game design
- Pearl collection gameplay
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Throw on your diving helmet, and head into the depths of the sea! Master the number line, including fractions and decimals, while gathering beautiful pearls. Will you find the elusive black pearl? • Ideal for elementary and middle school students, grades 3-8. Developed by mathematics educators, researchers, and game developers at the Learning Games Lab at New Mexico State University. Games developed by the Learning Games Lab undergo a rigorous instructional design process, extensive user testing, and input from learners, teachers, and researchers. Pearl Diver addresses Common Core standards relevant to the number line and properties of numbers, including: • Understanding numbers, ways of representing numbers, and number systems. • Understanding and representing commonly used fractions. • Understanding fractions as part of unit wholes and as locations on number lines. • Comparing and ordering fractions, and finding their approximate locations on the number line. For information about learning effectiveness, see the Math Snacks Research Summary: http://mathsnacks.com/research.html For information about the NMSU Learning Games Lab, visit http://learninggameslab.org. Developed as part of the "Math Snacks" initiative. Other free animations, activities, and games are available through the Math Snacks web site at http://mathsnacks.org. Math Snack materials were developed with support from the National Science Foundation (0918794). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Some materials were originally prototyped or discussed as part of a cooperative agreement from the U.S. Department of Education (U295A050004).
Stack Up
This educational app helps children aged 2.5 and up learn to arrange items by width. It fosters visual perception and primary math skills through engaging, simple activities. Designed for young learners, it avoids distractions and offers progress tracking for educators.
- Arranging items by width
- Develops visual perception
- Teaches primary math concepts
- Progress tracking for educators
- Safe for children
- Simple and intuitive design
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- Full version. - No in-app purchases. - No ads. - Safe for kids. Welcome to “Stack Up”. This educational app is designed for children aged 2.5 and above. Here children can learn to arrange items bottom-up according to their width. It is fun, and it helps them develop visual perception skills, and primary math concepts. STEP BY STEP is a professional EdTech studio that focuses on developing educational apps for children aged 1 to 5 years old. During these critical years, children enter a new learning stage every few months. Our apps support and strengthen the development of crucial skills for each learning stage. This way we guide your children, step by step, throughout this entire age range. Our key values are perfection and simplicity. We believe that small details make a big difference, so we give great attention to every detail — both in content and design. Most importantly, we keep our apps simple — simple to understand and simple to use. While playing our games, children will engage in simple activities, such as matching, pairing, ordering, grouping, and sorting. This allows them to practice essential skills, such as: categorization, conceptualization, generalization, abstraction, memory, language, math, visual perception, fine motor, accuracy, attention, and focus. They will learn about shapes, colors, animals, fruit, vegetables, clothing, tools, vehicles, furniture, professions, toys, etc., — all while playing. The levels are generally arranged by difficulty. The first levels are usually quite simple — their main objective is to teach players critical thinking and problem solving. However, the exercises become increasingly challenging as the child advances within the game. Our applications avoid distractions such as popups, unnecessary animation, and noisy feedback. We keep our applications safe for children — no advertisements, no unsafe links to external content, no popups, etc. Furthermore, our experience indicates that our apps can be very helpful for children with special-needs¹, and that they can function as useful tools in both speech-language therapy² and in occupational therapy³. In addition, our apps have been found useful for adults with disabilities or dementia⁴. For this reason, we added two important features: the first one was designed for teachers, therapists, and speech pathologists, which allows them to track the progress of their students; the second feature makes our apps also accessible for users with disabilities, and on this matter we would like to thank the Technology Consulting Center at “Beit Issie Shapiro”⁵ for their professional guidance and consultation regarding accessibility. ________ ¹ Special needs - Learning difficulties due to learning disabilities, communication disabilities, emotional or behavioural disorders, physical disabilities and/or developmental disabilities, which may be caused by Autism (Autistic Spectrum Disorders), Down Syndrome, Dyslexia, Tourette Syndrome, etc. ² Speech-language therapy - Treatment of communication disorders by speech-language pathologists (SLP). ³ Occupational therapy (OT) - Treatment meant to develop, recover, or maintain daily living and work skills for people with a physical, mental or developmental condition. ⁴ Dementia - A condition caused by brain injury (BI), brain damage or brain diseases, such as Alzheimer’s, Lewy bodies (DLB), Vascular dementia, etc. ⁵ "Beit Issie Shapiro" is a leading non-profit organization that develops therapies for people with disabilities, and also acts as a ‘Special Consultant’ to the United Nations.
Screenshots
Verdict
The clearest difference is rating: Stack Up at 5.0 against Pearl Diver HD's 1.5. Stack Up also leads on update cadence (every 2 months vs every 20 months) and review sentiment (100% vs 71%). On price, ads, in-app purchases and monetization model there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
Stack Up holds the better App Store score, 5.0 against 1.5. Both are backed by a comparable volume of ratings — 2 and 6 respectively. Written reviews point the same way: 71% of Pearl Diver HD's written reviews are positive against 100% of Stack Up's.
Pearl Diver HD ships an update every 20 months, Stack Up every 2 months. The most recent releases landed on November 1, 2026 and November 6, 2026 respectively.
| Parameter | Pearl Diver HD | Stack Up |
|---|---|---|
| Price | Free | Free |
| Rating | 1.5 (2 ratings) | 5.0 (6 ratings) — better |
| Positive reviews | 71.4% of reviews | 100.0% of reviews — better |
| Number of ratings | 2 | 6 — better |
| Update frequency | Every 20 months | Every 2 months — better |
| Ads | No | No |
| In-app purchases | No | No |
| Monetization | Free | Free |
| Devices | iPhone, iPad — better | iPad |
| Requires iOS | 17.6 | 7.0 — better |
| Further details — not scored | ||
| Size | 28 MB | 65 MB |
| Age rating | 4+ | 4+ |
| Developer | New Mexico State University Board of Regents | STEP BY STEP |
Customer experience
Pearl Diver HD
Stack Up
In-app purchases
Pearl Diver HD
No in-app purchases
Stack Up
No in-app purchases









