Haunted Cash Desk is a spooky interactive cash register built with the Rive CLI and RML. A Luau layout script drives a GPU Canvas fullscreen triangle shaded in WGSL: violet and magenta fog fills the scene, with orange embers near the floor and will-o'-wisp sparks. The register UI is written in RML: three drifting ghost receipts, a keypad and drawer, a neon HAUNTS LOGGED counter (data-bound), and a RING BELL button. Hovering turns the button bright magenta with a white stroke, a 1.22x scale and a purple glow ring. Clicking flashes the display and increments the haunt counter through a state machine and View Model write-back. Features used: Rive CLI, RML, GPU Canvas, WGSL shaders, Luau scripting, Data Binding, State Machines, Listeners. Built with an AI coding agent using a real verify, screenshot and publish loop with the Rive CLI. Play it: https://haunted-cash-desk-234rrm.rive.to Social post: https://x.com/maddiebrooksai/status/2107162720235876807 (Free-plan publish includes the Rive splash screen.)