# Kaijuengine Aidriver > Drive an already-running Kaiju game through its built-in AI Driver HTTP server (localhost, enabled by the `ai_driver` build tag): capture screenshots of the game window and inject mouse/keyboard input (click, type, scroll, key presses), loop screenshot then reason then act then re-screenshot, and quit the game gracefully. Use this whenever the user wants to look at, inspect, interact with, control, or visually verify the running kaiju game — for example "screenshot the game", "click the start button", "type into the name field", "is the menu rendering correctly", or "check my UI change in the running app" — even if they don't mention ai_driver or curl. Prefer this over the generic run/verify skills for a kaiju game that exposes the AI Driver server, since it talks to the live process via curl rather than launching or rebuilding it. Requires the game built with the `ai_driver` tag. - Skill: `kaijuengine/kaijuengine-aidriver` (Agent Skill) - Install (CLI): `npx skillmds@latest add kaijuengine/kaijuengine-aidriver` - Raw SKILL.md: https://api.skillmd.com/api/skills/kaijuengine/kaijuengine-aidriver/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: kaijuengine (https://skillmd.com/u/kaijuengine) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/kaijuengine/kaijuengine-aidriver --- # Kaiju AI Driver You control a running kaiju game by taking screenshots and injecting mouse/keyboard input through a localhost HTTP server compiled into the game. You talk to it with `curl`. No authentication; it binds `127.0.0.1` only. ## Preconditions The game must be running and built with the `ai_driver` tag: ``` go run -tags ai_driver . # or: go build -tags ai_driver -o game . && ./game ``` On startup it logs `AI Driver started addr=127.0.0.1:7777`. Default port is `7777`; override with the `AI_DRIVER_PORT` env var. Confirm it is up before doing anything else: ``` curl -s http://127.0.0.1:7777/v1/health ``` If this fails to connect, the game is not running or was built without `-tags ai_driver`. Ask the user to launch it that way; do not try to start it yourself unless asked. ## Coordinate & timing contract (do not violate) - **Coordinates are SCREENSHOT PIXELS, top-left origin (+x right, +y down).** Read a pixel straight off the screenshot you just looked at and send that exact pixel. The server converts to the engine's logical points for you — never multiply or divide coordinates yourself, even on a Retina display. - **Input takes effect over frames, not milliseconds.** A click is a press then a release on a later frame; typing is one character per frame. After acting, let the frame settle so the screenshot reflects your input: pass `settle_frames` (POST) or `?settle=N` (screenshot). `settle_frames: 2` is a good default. - Coordinates outside the framebuffer are rejected with `400 invalid_coordinate`. If the window may have resized, re-check `/v1/state` and re-screenshot. ## Core loop 1. **Learn the geometry** (once, and again after any resize): ``` curl -s http://127.0.0.1:7777/v1/state ``` Returns `window` (logical size), `framebuffer` (screenshot pixel size), `scale` (e.g. 2.0 on Retina), `focused`, and `frame`. The screenshot will be `framebuffer` pixels; send coordinates in that space. 2. **See the game** — capture a PNG to a temp file, then Read it: ``` curl -s "http://127.0.0.1:7777/v1/screenshot?settle=1" --output /tmp/kaiju-shot.png ``` Then use the Read tool on `/tmp/kaiju-shot.png` to view the frame. 3. **Reason** about what to do and note the target pixel from the image. 4. **Act and re-screenshot in one call** — POST input with `return_screenshot:true` and write the resulting frame straight to a file: ``` curl -s -X POST http://127.0.0.1:7777/v1/input \ -H 'Content-Type: application/json' \ -d '{"settle_frames":2,"return_screenshot":true, "actions":[{"type":"mouse_click","button":"left","x":1280,"y":980}]}' \ --output /tmp/kaiju-after.png ``` Then Read `/tmp/kaiju-after.png` to verify the result. 5. Repeat until the task is done. ## Resizing the window Resize the game window (dimensions are logical points, the same space as `/v1/state`'s `window`). Rendering pauses for a couple of frames while the window resizes and the swap chain rebuilds — the last frame is held on screen, so it's a brief freeze, not a flicker. The call waits for the new size to become stable before it returns, so the reported geometry (and any screenshot) already reflect the resize; you don't need to poll, but re-read `/v1/state` if you cached sizes. ``` curl -s -X POST http://127.0.0.1:7777/v1/resize \ -H 'Content-Type: application/json' \ -d '{"width":1600,"height":900}' ``` It returns `{"ok":true,"frame":...,"window":{...},"framebuffer":{...},"scale":{...}}` with the *actual* resulting size (the OS may clamp to screen or minimum bounds, so the height you get back can be smaller than requested). Add `"return_screenshot":true` (with `--output FILE`) to get the post-resize frame in one call, or `"settle_frames":N` to wait extra frames before the read-back. ## Closing the game When you are finished, shut the game down gracefully through the API instead of killing the process: ``` curl -s -X POST http://127.0.0.1:7777/v1/quit ``` It responds `{"ok":true,"message":"host is shutting down"}` and the game closes its window and exits on its own a couple of frames later. Do not use `pkill`. ## POST /v1/input reference Body fields: - `coordinate_space`: `"framebuffer"` (default; screenshot pixels) or `"window"` (logical points). Use the default. - `settle_frames`: frames to advance after the actions (default applied as-is; use 1-2 so a returned/next screenshot reflects the input). - `return_screenshot`: if `true`, the response body is the resulting PNG (use `--output FILE`); otherwise it is JSON `{ok, frame_after, actions_run, warnings}`. - `actions`: array, run in order, each spanning one or more frames: | type | fields | effect | |---------------|---------------------------------|--------| | `mouse_move` | `x`, `y` | move cursor | | `mouse_down` | `button`, `x?`, `y?` | press and hold | | `mouse_up` | `button`, `x?`, `y?` | release | | `mouse_click` | `button`, `x?`, `y?`, `hold_frames?` | press then release | | `scroll` | `dx`, `dy`, `x?`, `y?` | scroll wheel | | `key_down` | `key` | hold a key | | `key_up` | `key` | release a key | | `key_press` | `key`, `hold_frames?` | tap a key | | `type_text` | `text` | type a string (US-QWERTY) | | `wait_frames` | `frames` | idle N frames | - `button`: `left`, `middle`, `right`, `x1`, `x2`. - `key`: symbolic names, case-insensitive — `Return`/`Enter`, `Escape`/`Esc`, `Space`, `Tab`, `Backspace`, `Delete`, `Left`/`Right`/`Up`/`Down`, `A`..`Z`, `0`..`9`, `F1`..`F12`, `Home`, `End`, `PageUp`, `PageDown`, modifiers (`Shift`, `Ctrl`, `Alt`, `Cmd`). Examples: ``` # Type into a focused field, then submit curl -s -X POST http://127.0.0.1:7777/v1/input -H 'Content-Type: application/json' \ -d '{"settle_frames":1,"actions":[{"type":"type_text","text":"Player1"}, {"type":"key_press","key":"Return"}]}' # Press Escape and capture the result curl -s -X POST http://127.0.0.1:7777/v1/input -H 'Content-Type: application/json' \ -d '{"settle_frames":2,"return_screenshot":true, "actions":[{"type":"key_press","key":"Escape"}]}' --output /tmp/kaiju-after.png ``` ## Caveats - `type_text` is best-effort and assumes a US-QWERTY layout; symbols outside that layout and IME input are not handled. For anything non-alphanumeric, prefer explicit `key_press` actions. Unmapped characters are skipped and reported in the JSON `warnings` field. - If `/v1/state` shows `focused:false`, injected input may be ignored — ask the user to click the game window once to focus it. - The screenshot is the last *presented* frame, so always use a `settle` of 1-2 when you need to see the effect of input you just sent. - The server only moves the in-game cursor/keyboard — it cannot drive other apps or the OS, so its blast radius is the game window alone. ## Debugging ``` curl -s http://127.0.0.1:7777/v1/help # list endpoints curl -s http://127.0.0.1:7777/v1/state # geometry + focus + frame ```