OctoMinus is the latest switch-accessible app from Zyrobotics that allows children of all motor abilities to play arcade-style subtraction games. Like their earlier OctoPlus, OctoMinus is also designed to be fully customizable so that every child can experience success while playing and learning single-digit subtraction facts.

What we love…

Customizable gameplay that ensures more enjoyable play and learning experience for kids of all abilities.

What we’d love to see…

Direct access to the play options to change the speed of the turtles/octopus from within the game; on-screen indicator of how much ink is used/left for shooting; and game rules.


A fully customizable arcade-style subtraction game app that enables children of different abilities to experience success while playing and learning single-digit subtraction facts.

Our Rating

There are 2 modes of play in the app – Drill and Challenge. Each mode comes with a choice of 3 different skill levels – Beginner, Advanced or Expert. The objective of the gameplay in both Drill and Challenge is the same. A subtraction question appears at the top of the screen and the child has to use the octopus to shoot ink at the turtles to earn points.

While there are many arcade-styled subtraction apps in the app store, I want to highlight a few features in OctoMinus that you won’t find in most (if not all) of the other apps.


Firstly, instead of grouping the subtraction facts by the subtrahend (the number that is to be subtracted) in the learning mode (Drill) which is the typical approach, OctoMinus presents the facts by the subtraction difference (minuend – subtrahend = difference). For example, if you choose Drill 1, you will see all the subtraction equations that give you the answer ‘1’ e.g. such as 5-4 = ?, 10-9 = ? etc.

Secondly, To shoot ink, the child just needs to touch anywhere on the screen or use an external switch (connected through a Bluetooth switch). This makes it easy for children with motor difficulties or cognitive delays to play the games. As they gain more confidence and better skill, they can proceed to higher skill levels and adults can further fine-tune the difficulty level by adjusting the speed of the turtles and octopus in the Settings.

Other customisation options include turning off the sound effects, music, voice or background during the game if these are found to be affecting the players negatively. There is also a choice of English or Spanish language.


Most importantly, OctoMinus is all about success. In the Drill mode, kids will experience success all the time as all the moving turtles carry the answer to the subtraction equation. As long as you hit a turtle, you gain a point. The incentive for not tapping randomly is that if you use less ink, you earn more stars. The game ends when the time runs out. The constant audio and visual feed of the math facts goes into the childaren’s long-term memory as they play the games repeatedly. Although this app doesn’t teach your child how to subtract, it provides a stress-free way for learning the subtraction facts.


The Challenge mode is where players are tested on what they have learnt. For each subtraction equation that is presented, players touch the screen or switch to shoot the turtles when the octopus in the correct answer arch. There are 4 arches and 3 or 2 (instead of only 1) of them has the correct answer, again ensuring that the children have greater chance of success. They score points when they hit the turtles but face counter attacks from the turtles when they shoot from the wrong answer arch. Here, the number of correct and incorrect answers are recorded and summarised in the Math Score.


A detailed Progress Report of the last 5 Challenge play sessions is available in the locked Parents’ Zone and the information will give you an idea where your child needs more practice. The app also supports multi-player profiles which means you can have a few children using the app and all their progress reports are recorded.

Points earned by the players can be used to purchase sea creatures from the OctoStore for their Trophy Case which may be motivating for some children.

My youngest doesn’t fully understand how the Advanced or Expert skill levels work and how to strategise in order to get more points but I see that he enjoys the games. They don’t demand too much from him and he can experience success all the time. If you have a child who gives up easily when playing with games that are too hard for him/her, you should check out OctoMinus as you can customize the games so that your child will better enjoy the games and wants to play (practice) more. The games are also great for developing better fine-motor skills, hand-eye coordination, visual attention, reaction and timing.

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OctoMinus – Zyrobotics LLC

OctoMinus OctoMinus by Zyrobotics LLC
Category: Education, Games, Family, Arcade
Requirements: Compatible with iPhone3GS-iPhone-3GS, iPhone4-iPhone4, iPodTouchFourthGen-iPodTouchFourthGen, iPad2Wifi-iPad2Wifi, iPad23G-iPad23G, iPhone4S-iPhone4S, iPadThirdGen-iPadThirdGen, iPadThirdGen4G-iPadThirdGen4G, iPhone5-iPhone5, iPodTouchFifthGen-iPodTouchFifthGen, iPadFourthGen-iPadFourthGen, iPadFourthGen4G-iPadFourthGen4G, iPadMini-iPadMini, iPadMini4G-iPadMini4G, iPhone5c-iPhone5c, iPhone5s-iPhone5s, iPadAir-iPadAir, iPadAirCellular-iPadAirCellular, iPadMiniRetina-iPadMiniRetina, iPadMiniRetinaCellular-iPadMiniRetinaCellular, iPhone6-iPhone6, iPhone6Plus-iPhone6Plus, iPadAir2-iPadAir2, iPadAir2Cellular-iPadAir2Cellular, iPadMini3-iPadMini3, iPadMini3Cellular-iPadMini3Cellular, iPodTouchSixthGen-iPodTouchSixthGen, iPhone6s-iPhone6s, iPhone6sPlus-iPhone6sPlus, iPadMini4-iPadMini4, iPadMini4Cellular-iPadMini4Cellular, iPadPro-iPadPro, iPadProCellular-iPadProCellular, iPadPro97-iPadPro97, iPadPro97Cellular-iPadPro97Cellular, iPhoneSE-iPhoneSE, iPhone7-iPhone7, iPhone7Plus-iPhone7Plus, iPad611-iPad611, iPad612-iPad612, iPad71-iPad71, iPad72-iPad72, iPad73-iPad73, iPad74-iPad74, iPhone8-iPhone8, iPhone8Plus-iPhone8Plus, iPhoneX-iPhoneX
Size: 167.2 MB


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NOTE: A fee was received to expedite this review to the top of our waiting list but this payment has not influenced the objectivity of the review and all opinions have been offered honestly.

Grace was working in the fields of early childhood education and staff training before quitting to attend to her 4 children full time. She and her family live in Singapore, which is well known for her highly competitive education system.

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