From 2 battles to 90 spirit forms: building KINBOUND with GPT-6 Astra

Hi Product Hunt! I'm Kevin, the maker of KINBOUND.

I started with a small, two-battle spirit-card prototype. Using GPT-6 Astra through Codex, I expanded it into a browser adventure with three chapters, 18 stages, 30 collectible spirits and 90 forms.

The core idea: see the enemy's next move, then build your answer. Bring a team of three, manage energy, play tactic cards and switch your front line. Each spirit has two evolution branches with different strengths and tradeoffs.

You can play free now, with no account required:
Play the KINBOUND campaign

There are English and Chinese interfaces, local autosaves with import/export, and a separate invite-link mode for battles with a friend. Friend battles currently use six starting spirits; the 30-spirit collection belongs to the solo campaign.

What Astra contributed: expanding the design, implementation, debugging and validation. The released version passed 173 automated tests alongside browser playthroughs. Battles follow deterministic rules; the public game doesn't call an AI model while you play. Creature artwork was pre-generated with Image Gen.

KINBOUND is scheduled to launch on Product Hunt on September 18 for the GPT-6 Astra Challenge. Before then, I'd love some honest playtest feedback:

• Was the enemy-intent system clear in your first battle?

• Which evolution choice felt interesting, or confusing?

• Which three spirits would you put on your team?

A quick first impression or a screenshot of a confusing moment would be especially useful. Thanks for trying it!

Promotional artwork featuring three of the spirit companions: