Culebra

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.

Make me the snake game for the browser.

- The snake moves on its own on a 20x20 grid and I only change direction; it can't turn back on itself.
- Each fruit makes it one cell longer and is worth 10 points. Every 5 fruits it gets a little faster.
- I lose if I bite my own tail. Hitting the edge brings me out the opposite side.
- Screens: title with a Play button, the game with score and high score, and game over with a retry button.
- Controls: arrow keys or WASD on desktop; swipe on mobile.
Technical: a single HTML file with the CSS and JavaScript inside, no libraries and no external images, everything drawn on canvas. It should fill the window and be playable with a finger on a phone and with keyboard or mouse on a computer.

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.

Hazme un juego de navegador llamado "Culebra".

La idea: el clásico juego de la culebra que come y crece, con arte original y un acabado moderno.

Mecánica:
- La culebra avanza sola en una cuadrícula de 20 x 20 casillas. El jugador solo cambia la dirección; no puede darse la vuelta en seco.
- Cada fruta que come la alarga una casilla y suma 10 puntos. Cada 5 frutas la velocidad sube un poco.
- Cada tanto aparece una fruta dorada que dura 5 segundos y vale 50 puntos.
- Pierdes si chocas contra tu propio cuerpo. Con "paredes" activadas, también al chocar con el borde; sin ellas, sales por el lado contrario.
- Tres velocidades a elegir al empezar: lenta, normal y rápida.

Pantallas: título con Jugar, la velocidad y el interruptor de paredes; el juego con HUD (puntaje, récord); pausa; y fin con el puntaje y un botón para reintentar.

Controles: en PC, flechas o WASD para girar y Espacio para pausar. En celular, deslizar el dedo hacia donde quieres girar (en cualquier parte de la pantalla) y tocar para pausar.

Estilo: fondo verde oscuro con la cuadrícula apenas marcada, culebra con degradado de la cabeza a la cola y ojos que miran hacia donde va, frutas rojas que laten, y partículas al comer.

Técnico:
- Un solo archivo HTML con todo el CSS y el JavaScript dentro. Sin librerías, sin CDN, sin imágenes externas: todo dibujado en canvas.
- Tiene que llenar la ventana y adaptarse a cualquier tamaño, de celular a pantalla grande, sin deformarse.
- Tiene que jugarse completo desde celular (solo con el dedo) y desde PC (teclado o mouse).
- Tiene que funcionar dentro de un iframe con sandbox="allow-scripts". El récord va en localStorage dentro de try/catch para que el juego no se rompa si no hay acceso.
- Se pausa solo cuando la pestaña no está visible.
- El texto del juego va en español.

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.

• Say whether the golden fruit also makes the snake longer and whether it counts toward speeding up: the prompt didn't, so the AI decided.
• Ask for one high score per mode (speed and walls make 6 different combinations), or accept a single high score for all of them.

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

• Agrégale un menú de pausa, un botón para cambiar entre español e inglés, y que el récord no se pierda al recargar.

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