Kuru

Ask for it like this

Copy this prompt, paste it into Claude or ChatGPT, and that's it. It's the short version: the minimum for the game to come out playable.

Hazme un juego de gusanos para navegador, al estilo de los juegos de gusanos en línea donde uno crece comiendo, con nombre y arte originales.

- Una arena grande y redonda llena de bolitas de colores. Mi gusano sigue al mouse (o al dedo) y crece al comer.
- Puedo acelerar manteniendo el clic: voy el doble de rápido, pero pierdo largo y dejo bolitas atrás.
- Si mi CABEZA toca el cuerpo de otro gusano, me muero y mi cuerpo se vuelve bolitas para los demás. Si otro choca su cabeza contra mi cuerpo, se muere él.
- Bots que buscan comida, esquivan y a veces intentan cortarme el paso, para que la arena siempre esté llena.
- Cámara que sigue a mi gusano, minimapa y tabla de los 5 más largos.
- Modo en línea con código de sala para jugar con amigos en la misma arena.
Técnico: un solo archivo HTML con el CSS y el JavaScript dentro, sin librerías ni imágenes externas, todo dibujado en canvas. Que se vea suave a 60 cuadros por segundo y se juegue con el dedo en el celular y con mouse en la PC.

This one is still in Spanish. Paste it as is (the AI understands it) and add "Answer in English" at the end.

Getting it as an HTML file

A game like this is a single file you open with a double click. These four steps are the same in any AI.

1. 1. Ask for the whole file

   Add this line at the end of your prompt: Give me a single, complete HTML file, nothing cut out, ready to save as index.html and open in the browser. Without it, you often get the code in pieces.

2. 2. Copy all of the code

   In Claude the game shows up on the side, already running, with a button to copy or download it. In ChatGPT, copy the whole code block: it has to start with <!DOCTYPE html> and end with </html>.

3. 3. Save it as index.html

   Paste it into Notepad (Windows) or TextEdit in plain text mode (Mac) and save it as index.html. Watch out for .txt: if the file ends up as index.html.txt, it won't open as a page.

4. 4. Double-click to open it

   It opens in your browser and it's ready to play, with nothing to install and no internet needed. To share it, upload it to any web host or send it by email: it's just one file.

If the game shows up blank, go back to the AI and paste the error from the browser console (right click → Inspect → Console). With that text it fixes it fast.

The full prompt, the one actually used

Longer and more specific: numbers, screens and style details. It's the one that produced exactly this game, unedited. Use it if you want to fine-tune the result.

Diego wrote it in Spanish and it stays in Spanish on purpose: it's the honest record of how the game was made, and a translation would be a prompt nobody used. Claude and ChatGPT understand it as is; add "Answer in English" if you want the game's text in English.

el otro multiplayer que era bueno era ese como gusanito pero multiplayer y que ibas creciendo no recuerdo como se llama porque comias bolitas del escenario y tmabien si se chocaban contigo su cabeza se morian y dejaban bolitas para comer

For ChatGPT, add the line from step 1 at the end: it tends to hand over the code in pieces.

What this prompt was missing

What became clear once the game was finished. If you're making your own from this one, add these from the start: fixing things later costs another round.

• Ask from the start for movement to look smooth at 60 frames (the body as a single stroke, a tail that slides, no blurry sprites): the first version jittered and the drawing had to be redone.
• Say how many people fit in a room and what happens if the host leaves: in this kind of game the arena lives in one person's browser, and players need to know that.
• Naming the reference game helps with the mechanics, but you have to explicitly ask for an original name, art and characters.

What was asked after the first result, in Diego's own words (Spanish):

• se ve el cuerpito como si vibrara, se ve raro, como que las bolitas tienen un blur, quiero que sea smooth

It works in any AI

Claude, ChatGPT, Gemini, Copilot: the prompt is the same and so is the method. What changes is where you see the result. Four things that hold in all of them:

1. Ask for a single file

   "A single HTML file with everything inside, no libraries or CDN." That way the game works with a double click, with nothing to install, and you can upload it to any website.

2. Ask it to tell you what it assumed

   End with: "before writing the code, tell me in 5 lines what you assumed". That's where the gaps in your prompt show up, while fixing them is still cheap.

3. One fix per message

   Say what happens and what you expected. If you ask for three changes at once, one usually undoes another.

4. Ask it to test, not to promise

   "Check that every level can be won and tell me how you checked." That's how the games on this page found their bugs before going live.

The 6 parts of a good prompt, with a template to copy