Collaborative koloring with Kotlin
summary
A collaborative pixel-canvas is built end to end in Kotlin: a Ktor server using Ktor + Kotlin coroutines and WebSockets, a Kotlin/JS frontend with Kotlin/JS + React wrappers, and Redis-style key hashes for storage. Each paint checks a per-user cooldown, updates a single cell in the DB, then broadcasts to all clients (no optimistic local-only updates). Build runs on Heroku; frontend tooling blows the JVM heap during compilation (needed ~4GB). The live demo works and users are already drawing; winners are decided by final colors.
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