# Coin-Flip Duel
> ⚠️ **Experimental — generated with no human supervision.** This realm was
> produced automatically by an MCP-driven agent to exercise the gno MCP server
> and tooling, and to generate test content for gno compilers, linters and
> formatters. **Not audited. Not for production.** Full context & folder README:
> [r/moul/x/daily](https://github.com/moul/gno-contracts/blob/main/r/moul/x/daily/README.md)
---
A one-on-one coin-flip duel between two addresses. The challenger picks
heads or tails and names an opponent; the opponent settles it with a single
`Accept` call, which flips the coin on the spot and records the result. No
stakes, just an on-chain win/loss record and a running champion.
Realm: `gno.land/r/g12cs4cehujpffpjpywmkqj43m6u5ya53nj69sjz/coinflipduel`
## Example calls
```
Challenge("g1bob...", "heads") # as alice -> opens duel #1, alice called heads
Accept("1") # as bob -> flips the coin, settles the duel
Cancel("2") # as the challenger, before it's accepted
```
## Render paths
- `` (home) — arena summary, champion, pending duels
- `<id>` (e.g. `3`) — a single duel's detail
- `<address>` — a player's win/loss record
## Toolchain
Built and tested against the local `gno` binary (`master.3130+bf5b31eda`).
`gno test .` passes; see the injected build brief for the sapphire (gno 0.9)
API notes this realm follows (`chain`, `chain/runtime`, `gno.land/p/nt/avl/v0`).
## What changed in v1
Identical behaviour to [`v0`](https://github.com/moul/gno-contracts/tree/4f2df83869b80470eb81c48a82fdbe82256b8113/r/moul/x/daily/coinflipduel) apart from rendering, which now goes
through [`p/moul/kit/ui`](/p/moul/kit/ui/v0) instead of the local `escapeInline` helper.
**Real escaping.** The local helper replaced a handful of markdown metacharacters. `ui.Inline` and `ui.Cell` delegate to [`p/nt/markdown/sanitize`](/p/nt/markdown/sanitize/v0), which also strips bidi and zero-width characters and folds newlines, so user text cannot reorder or escape the line it sits on.
The rendering change means the output differs from v0, which under this repo's versioning rule is a compatibility change, hence a new version rather than an edit in place. `v0` stays live and untouched.
<!-- BEGIN GNOCONTRACTS FOOTER (generated by `make readmes`; do not edit below) -->
---
Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.
**Dependency graph:**
> 🧪 **Highly experimental — potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).
<!-- END GNOCONTRACTS FOOTER -->
Accept(cur interface {.seal func(); Address func() .uverse.address; IsCode func() bool; IsCurrent func() bool; IsEphemeral func() bool; IsUser func() bool; IsUserCall func() bool; IsUserRun func() bool; PkgPath func() string; Previous func() .uverse.realm; String func() string; Sub func(string) .uverse.realm; Subpath func() string}, id string) string
Cancel(cur interface {.seal func(); Address func() .uverse.address; IsCode func() bool; IsCurrent func() bool; IsEphemeral func() bool; IsUser func() bool; IsUserCall func() bool; IsUserRun func() bool; PkgPath func() string; Previous func() .uverse.realm; String func() string; Sub func(string) .uverse.realm; Subpath func() string}, id string) string
Challenge(cur interface {.seal func(); Address func() .uverse.address; IsCode func() bool; IsCurrent func() bool; IsEphemeral func() bool; IsUser func() bool; IsUserCall func() bool; IsUserRun func() bool; PkgPath func() string; Previous func() .uverse.realm; String func() string; Sub func(string) .uverse.realm; Subpath func() string}, opponentAddr string, call string) string
Render(path string) string
Signatures reconstructed verbatim from vm/qfuncs — interface params keep their inline definitions.
vm/qrender output, sanitized (docs/render-security.md) and displayed in an empty-sandbox iframe — scripts, forms and popups cannot run. Links stay inert in-preview; right-click to open.