Show HN: Ball 2 – Use AI to build fun ball games

[klangdon]

I wanted to find a way to get kids:

- moving

- creating

- playing with others

In the end I, and a team of 4 others, built:

- a foam ball with a BLE IMU in it (moving/together)

- an app that allows you to create almost any game you can imagine with AI (creating)

Video of teenagers making a game: https://www.youtube.com/watch?v=-7TZXRBybOE

Video that was intended to be for Kickstarter: https://www.youtube.com/watch?v=Edy9zew1XN4 (we abandoned kickstarter, long story)

For hardware we came up with a pretty awesome custom PCB, based around a Dialog DA14531, that doesnt need any charging for over 500 hours of play. The electronics are encased inside 4.5" diameter of foam. We drove a car over it and it didn't break.

For the app, we are using OpenAI Realtime API (gpt-realtime-2025-08-28) to gather the game requirements via conversation. We are using voice/realtime to allow kids to do it without needing to type or read. This piece has a huge dynamic prompt that flows with the conversation. It has about 20 different tools that the agent can use to access sample requirements, ball data, user profiles, api documentation, etc. We also did a lot of work to require younger kids to have adults present and make sure we never saved any pii, etc.

Then we use Gemini 3 Pro to process the conversation and generate a markdown specification/arhictecture of how the game should be designed. We found that Anthropic Opus 4.6 did perform better here, but Gemini 3 Pro is much cheaper and faster. This has a static/cacheable prompt that is primarily a ball api documentation and details on previously seen issues.

Then we use Gemini 3 Pro to also code the game. A very similar prompt to the specification/requirements just different purpose. We are currently exploring condensing the architecture and coding steps into a single step, with new "thinking" models. Also seeing that Google is launching 3.1 model, literally while I type this...

The end result is an app that allows you to speak game requirements, have ai code the game, then you get to play it with a real physical ball.

So ya, tons of fun building all that. Curious what HN thinks. Now the hard part of maybe getting someone to buy it...

[BretJohnson]

This looks like a fun product I suspect my 7 year old would love. We're also just beginning to teach him to code (using scratch with Lego Prime and Makey Makey) so it would be cool if there were future plans to allow kids to code their own games around the ball and the amazing in-built sensors-or to be able to explore the AI generated code and play around with it.

One glaring call out for me as a parent looking at the product itself -- the in app purchase. Wanted way more clarity around those.

For instance it wasn't super clear how many credits would typically be used when creating and dialing in a game (my 7 year old is unlikely to be super efficient in prompts!)

The biggest issue though was I couldn't find the cost of in-app credit purchases listed anywhere. I wouldn't go near a product like this without being able to wrap my head around the scope of on-going costs.

Perhaps highlighting the existing number of free-to-play games would show the value proposition apart from the AI coding aspect. Better yet, provide a way for potential buyers to explore that database and see for themselves how many great, diverse options exist?

Site looks great and really made me want to give it a go.

Cheers from New Zealand...where I'll either consider myself on the waitlist for international delivery, or add it to our 'ship to parents and pick up when in the US list'

-Bret

[klangdon]

Thanks for the feedback. Great that you are teaching your child to code. For education purposes, I think our first step will be exposing the code that the AI is generating and then next allowing editing it.

It is true we need to be more clear on the game credits.

Currently you can create 20 games with cost of the ball. Then it is $5USD to create 10 games and $6USD per month for unlimited games.

You can remix/improve any of those games for free. The cost of this component is a little unknown to us.

We really are only looking to only cover our AI token costs on game creation. This will likely change if we add text only ability to create games. Right now the realtime/voice part of it is like 80% of our cost.

[BretJohnson]

Personally, those rates seem very reasonable and I wouldn't shy from making that more clear.

1) I love that it isn't strictly locked into a subscription model but could be either pay as you go or pay monthly

Paying monthly would remove my stress of his usage and if it was clearly set up as a 'pause any time' subscription model I'd be even more inclined. Ie. He may be REALLY into it for a month or two and then hard pivots to a new thing so being able to pause easily month-to-month while I wait for his attention to cycle back is a great thing.

2) I think you could also explore saying, 'We know AI is moving fast and their models are always evolving, we're committed to offering credits to our amazing community at fair market rates plus a Ball2 platform fee of 10% which helps us improve Ball2 and add more features. And since we're able to pool the buying power of the whole Ball2 community, we hope to keep the cost of creating as low as possible. Currently those rates are...'

I think you're also set up to offer a really incredible maker community as kids share their games and iterate off one another. If you don't have plans for a basic community forum I'd lean in to that. Would be cool to sponsor monthly challenges or organize mini-hackathons where kids spend a weekend collaborating virtually to come up with new more elaborate games or solve design challenges that employ the balls capabilities etc. -- Also helps keep kids engaged and using credits ;) or looking forward to Ball3!

I could also see you offering school stem kit packs or school PE packs etc.

What a really cool space to be playing in.