Try a new kind of math game in line with the Math Revolution envisioned by innovators like Youcubed and AOPS. Designed especially for children 6-11, "21 Marbles" doesn't quiz or time the player, instead it let's them enjoy thinking and reasoning.

A puzzle game's level progression is a natural "low floor, high ceiling" exercise. In the case of 21 Marbles, while the puzzles can become challenging enough to be enjoyed even by adults, the game has a friendly progression of difficulty that keeps everyone on board.

For the youngest players, it has the additional benefit of practicing the most basic arithmetic facts in an instinctive way. For the adults, it's like a relaxing peg solitaire game.

There are no instructions because the rules are natural and intuitive. 21 marbles - of colors and designs for all tastes - are won one by one. In every level, the recovered marbles - each representing the number 10 - break randomly into pairs of smaller marbles: either into a 9 and a 1, or an 8 and a 2, or a 7 and a 3, or a 6 and a 4, or two 5s. The marbles get positioned randomly on a board, and can be merged back together into 10s, by knocking together pairs that sum to 10. It is always possible to recover all 10s, but some thinking ahead is required. The "undo" button is always there to let you trace back your steps and find your mistakes. Learning to think ahead is not optional, and is the most important educational aspect of this game.

What’s New

Version 2.0.1

Sharing your progress with friends is now a click away. Actually, a click and a parental gate away, to be exact.

Ratings and Reviews

4.5 out of 5
105 Ratings

105 Ratings

Flywithkids ,

Fun for all ages!

My daughter (age 9) played it till level 16, and I took up where she left off and completed it. It had a simplistic user interface but don’t let that fool you. The idea of the game is compelling like that of Tetris or the Chinese card game of 24. And the gameplay had pauses that let the mind rest a little. Kids of all ages will enjoy the earlier levels and grown-ups will enjoy the later levels.

Ilandria Second ,

Relaxing and challenging

I’m always looking for unique and challenging games. Here, I found a challenge that allowed me to relax into it.

Highly recommended!

SoxShadow ,


You should be able to play more than twenty one levels.


Elitza Maneva
51.6 MB

Requires iOS 8.0 or later. Compatible with iPhone, iPad, and iPod touch.


English, Basque, Bulgarian, Catalan, Czech, Dutch, Finnish, French, German, Hebrew, Indonesian, Italian, Japanese, Korean, Malay, Norwegian Nynorsk, Polish, Portuguese, Russian, Serbian, Simplified Chinese, Slovenian, Spanish, Swedish, Traditional Chinese, Ukrainian

Age Rating


  • Family Sharing

    With Family Sharing set up, up to six family members can use this app.

You May Also Like