warm-up · day 4

Come up with your own game

The warm-up is over. Choose the game you want to take through to release, with your own genre, setting and tone. Start from scratch or keep an idea you tried in the first three days. The agent will help record your decisions and build a first draft.

⏱ your time 75 min🎮 ends with your own gameyou need: the agent and tools from Getting ready or the quick start

by the end of the day

sketch.html: a one-screen draft with the main action, obstacle, win and loss
GAME.md: eight decisions, two rules and the size of your game
your own folder ~/games/my-game and version day-04
To try it: ask to open sketch.html and play a round

Dino, Bird and Snake have done their job. You can leave them in first-game and never return to them. Your main project lives separately in my-game. The lesson examples are suggestions; your game doesn’t need their characters, setting or rules. We keep the scope small so you can finish. The tone and subject are yours to choose.

If you already have an idea, check the genre and art method in step 2, then create your game folder. Try the exercises in steps 3 and 6 as well: they help pin down the idea.

Came via the quick start?

You can skip step 1, which uses the remix from days 2–3. Create your notes in step 4 and skip the remix settings in step 8. The working habits we use later are in the quick start.

One more round in yesterday's game

Open your remix, press P and play for a minute. Remember which settings you chose and why.

Open remix.html in the browser.

A quick recap

The hero left the edge a moment before you pressed jump. Which setting could help?

Increase the jump heightThe jump never started because the press came after the edge. Height will not fix that.
Add about 0.1 s of coyote timeYes. It gives you a short window to jump after leaving the edge.
Shrink the hitboxThat affects collisions. Here, the jump input arrived too late.

You adjusted two sliders and the jump improved. What is still unclear?

Whether the panel allows two changesIt does. But the test does not tell you what each number contributed.
Which number helpedRight. Put one back to its old value and compare.
How to get the old settings backReloading restores the CONFIG values, but it does not tell you which change helped.

By tonight

One lineyour idea

Interviewagent asks, you choose

GAME.mdyour game on one screen

sketch.htmlyour game's draft

Yellow marks your decisions; green marks the agent's work. First, choose the game you want to make.

Choose a genre

Your genre and art method determine the examples and homework you will see. If you picked them earlier, check your choices and carry on.

How your game will look

no extra cost

Model to match

target picture
3D models in Blender
frame with a filter

what you get: A world matching the picture you pick on day 7: cartoon, pixel, painterly or low-poly.
how it works: The agent builds a 3D world; a style filter makes it look drawn, and camera and light match your picture. Like the fighting game Guilty Gear Xrd: 3D inside, drawn on screen.
what you need: Free Blender: you install it on day 8, the agent uses it.
cost: No extra cost for art.
who it's for: No budget for art; you like dioramas, pixels, cartoons.

paid or on your own PC

AI paints it

pictures from AI
finished 2D scene

what you get: A hand-drawn 2D world: hero, enemies, backgrounds and UI in one style. The hero is animated like a puppet or from video.
how it works: AI paints; code animates and lights. To keep the hero consistent, each request repeats the same style phrases (an anchor) and samples.
what you need: One of three ways: ChatGPT Plus, the API paid per picture, or your own computer with an NVIDIA card with 12 GB or more. With Plus, you carry its requests to ChatGPT by hand. With Plus, Codex draws by itself.
cost: ChatGPT Plus: $20 a month, on top of Claude Pro: already have it? No extra cost, but limits go faster. The API has no monthly fee: first top-up from $10; we estimate $1–3 for all the game's pictures, and optional hero clips add $1–4.5. On your own computer there's no extra cost, but you wait longer.
who it's for: You want a hand-drawn look: painting, watercolor, detailed characters.

The best approach is to combine them. For example, build the world as a model, let AI paint the hero, and make the animation clips on your own computer.

The lessons follow one main route so the steps don’t get mixed up, but in your own game you can combine them. You can still change the main route before the project step on day 5.

What we will make in this genre

By the finale: 6 levels of 30–60 s plus an ending screen, about 5 minutes.

In “Model to match”: the hero moves on a plane, the camera looks from the side, and the scenery has depth.

Start with one ability you enjoy using. We will build levels around it.

In the interview, ask what one ability the hero has besides jumping, and suggest 3 options.

By the finale: a 5-minute run: 4 waves and a boss at minute five, 6–8 upgrades to choose from.

In “Model to match”: an angled overhead camera shows the field and a hundred enemies as a 3D diorama.

Think about what the player chooses between waves and how that affects the next fight.

Ask about the run length (I suggest 5 minutes) and the first 3 upgrades to choose from.

By the finale: 8 levels: the first 3 teach, the twist starts at level five.

In “Model to match”: the board looks like a tabletop puzzle, viewed from a distance.

Start with one rule and find different problems you can build from it.

Suggest 3 grid puzzle rules, one sentence each, and show the first level as rows of text.

By the finale: 3 fights and a boss; 8 cards at the start, 15–18 in total.

In “Model to match”: cards sit on a table, with pictures made from screenshots of game models.

The player should understand what a card does before playing it.

Ask which 8 cards make up the starting deck, and suggest 3 sets.

By the finale: one map, 3 waves, a win at minute five.

In “Model to match”: an angled overhead camera looks across a 3D map.

Start with one resource, two buildings and three units. Check that giving orders feels comfortable.

Ask about the single resource and 3 unit types, each stronger than one and weaker than another.

By the finale: 5 in-game days, the goal is saving up for a big purchase.

In “Model to match”: your garden, kitchen or shop looks like a tabletop diorama with warm light.

Give the player a goal without a way to lose, such as saving for a purchase.

Ask what big purchase the player is saving for and what they do every day.

By the finale: 8–12 scenes, 3 choices with consequences, 2 endings.

In “Model to match”: a live 3D diorama sits behind the text, like an animated book illustration.

Choose the player's role and the decision they will make most often.

Ask who the hero is, what they want and what choice they'll have to make again and again.

By the finale: 3 rooms and an exit.

In “Model to match”: a 3D world viewed from above or through the hero's eyes. “AI paints it” gives you a hand-drawn top-down game.

Start with one arena and one weapon that feels good to fire.

Ask about one room for the draft and one weapon; the draft is top-down.

By the finale: a village, a 3-room dungeon and a boss; one main quest and one side quest; 3 hero levels.

In “Model to match”: the village is a 3D diorama viewed from an overhead angle.

Make the hero's growth noticeable to the player.

Ask what the hero levels up and what one quest leads them into the dungeon.

Your chosen genre is already included in the interview prompt.

What one sentence leaves for the agent to decide

You can tell the agent “make Vampire Survivors underwater” and it will build something. But it will have to pick the hero, the action, the obstacles and the length on its own. Better to decide those together.

Below are three such lines from different genres. Press “Hand it to the agent”, then swap in your own calls on the cards. It's just practice: you'll take apart your own idea the same way in the interview.

try itOne line, eight decisions

Green: the agent's picks, the internet average. Yellow: your calls. On the sketch, gray is someone else's decision, color is yours.

One line is a fine start if you spin it out yourself. Arvi Teikari made Baba Is You at a jam themed “Not there”. That made him think of logical NOT and gave him “a mental image of pushing words to create rules” (Game Developer, 2018).

You asked for “a lighthouse game” and got a finished draft. Who chose the number of levels?

The agent; I did not specify itYes. It had to fill in the parts missing from your request.
I did, because it was my ideaThe idea is yours, but the level count is a separate decision you had not made.
Nobody has chosen that yetThe finished draft already has some number of levels. The agent chose it.

Create a folder for your game

Keep your remix in first-game. Create ~/games/my-game for the new game and open the agent there, so the files stay separate.

Leave the old chat with /exit, then paste the command for your system into the terminal:

macOS and Linux

mkdir -p ~/games/my-game && cd ~/games/my-game && claude

Windows

mkdir ~\games\my-game -Force | Out-Null; cd ~\games\my-game; claude

Leave the old chat with /exit, then paste the command for your system into the terminal:

macOS and Linux

mkdir -p ~/games/my-game && cd ~/games/my-game && codex

Windows

mkdir ~\games\my-game -Force | Out-Null; cd ~\games\my-game; codex

New sessionStart in the Code tab, environment Local.
New folderFolder picker → Open folder… Inside games, create my-game and pick it.
ModeAuto, or Accept edits if there's no Auto.

New folderChoose Open folder (on a Mac, Cmd + O). Inside games, create my-game and pick it.
Where to workIn the Work in switch keep This computer, mode Ask for approval.

If the agent asks whether you trust the folder, check that it is my-game and confirm. Then create the notes file. If you did this on day 2, the prompt will look familiar; it adds one line for the new game.

Create a file CLAUDE.mdAGENTS.md in this folder: notes for you. You read it at the start of every chat. This is my game's folder. Write down 6 rules: 1. Answer in plain English, in simple words. A technical term only with an explanation in brackets. 2. One change at a time. If I ask for two, do the first and ask about the second. 3. Keep all the game's numbers in a CONFIG object at the top of the script, each with a plain-English comment. 4. After a change, open the game and tell me in a line or two what I should notice. 5. Save only when I say “save”. Before saving, tell me which files changed. 6. Don't touch files outside this folder. Keep the notes under 30 lines. Show me all of it.

Check that the agent has opened ~/games/my-game and created notes in that folder.

How to check:

Asked “Which folder are you in?”, the agent names a path ending in my-game
The agent showed the notes, with the line “This is my game's folder”

If the agent says first-game, close it and restart in the new folder using the instructions above.

Talk through the idea

Have the agent ask questions with answer options while you choose what the game will be. The prompt already includes your genre and art method. Replace “[my idea]” with yours, such as “a rookie cook keeps a night noodle bar going until closing”. Any topic and genre will do; you don't need to repeat the lesson's examples. If you have no idea yet, ask for three suggestions.

Help me come up with my first game. Genre: [my genre]. One-line idea: [my idea]. If there's no idea, suggest 3 of your own in this genre, and I'll pick. Ask me questions first, don't write code: - two rounds of 5 questions at most; - each question has 3–4 options: first the one you recommend, marked “recommended”, last “my own answer”; - ask only about what the player decides: hero, main action, goal, obstacle, lose, win, length, mood. Don't ask about tech, decide that yourself. - also ask about the camera: side view, angled from above, from afar like a tabletop diorama, over the shoulder or first person. Offer the one that fits the genre first; for a platformer it's side view, and the game plays on a flat plane. We'll match the camera to my picture later. - ask what one ability the hero has besides jumping, and suggest 3 options. - ask about the run length (I suggest 5 minutes) and the first 3 upgrades to choose from. - suggest 3 grid puzzle rules, one sentence each, and show the first level as rows of text. - ask which 8 cards make up the starting deck, and suggest 3 sets. - ask about the single resource and 3 unit types, each stronger than one and weaker than another. - ask what big purchase the player is saving for and what they do every day. - ask who the hero is, what they want and what choice they'll have to make again and again. - ask about one room for the draft and one weapon; the draft is top-down. - ask what the hero levels up and what one quest leads them into the dungeon. After the interview, create GAME.md, my game on one screen: the one line; eight decisions (put the answer to the genre question into the one that fits, e.g. “Main action”) and a line “Look: AI paints it (2D)Model to match (3D, camera …)”; two game rules in the form “the player feels …; broken if …”; what's not in the game; the scope for 5 minutes of play, in numbers. Mark who made each decision: “my call” or “agent's call”.

Questions may appear as buttons or text. A short text reply is enough: “1A, 2B, 3 — my own: the broth boils over if you look away”. If you are unsure, take the recommendation and revisit it later.

The player's role decides a lot. Lucas Pope on Papers, Please: you're not the hero slipping across the border but the guard checking documents (Game Developer, 2014). New role, new game.

After the questions, the agent records the decisions in GAME.md. Here's a sample for someone else's idea; yours will have its own hero and world:

GAME.md

# Noodles Till Closing ## One line A rookie cook feeds the line at a noodle bar window all night and finishes before closing. ## Eight decisions - Hero: a rookie cook on their first shift — my call - Main action: builds each bowl to order from three ingredients — my call - Goal: feed 30 guests in one night — my call - Obstacle: orders get longer, the broth boils over — my call - Lose: three guests leave hungry — my call - Win: the last bowl goes out before closing — agent's call - Length: 3 nights, a minute and a half each — agent's call - Mood: a rainy night, the warm kitchen light — my call Look: AI paints it (2D)Model to match (3D, angled overhead camera) ## Two game rules 1. The player feels they can keep up if they stay calm; broken if an order burns before they can read it. 2. The player sees at a glance what's missing from a bowl; broken if ingredients get mixed up by color. ## Not in the game Open world, online play, a shop. ## Scope for 5 minutes 3 nights, 5 ingredients, 8 kinds of orders, an ending screen.

Check all eight decisions. Most should be choices you made.

How to check:

GAME.md is in the folder and fits on one screen
Eight decisions, each marked “my call” or “agent's call”
No more than three “agent's call”

If the agent starts coding, stop it: “Questions first, code later.” If it asks about engines or other software, say, “Choose the technology yourself; ask me about the game.”

Choose a game you can finish

Now check the size of the game. We are aiming for about 5 minutes on a first playthrough and 10 evenings of work. Add features to the backpack and watch both meters. Keep them in the green without overfilling it.

try itA backpack for five minutes

Each card shows the minutes of play it adds and the evenings it eats. Estimates, not laws.

When you like the selection, press “copy” beneath the backpack and send the task to the agent.

Compare the “Scope” section in GAME.md with my backpack: [the list from the backpack]. Move everything that didn't fit into “Not in the game”. Show me both sections.

The Chrome dino lost its roar and kick, keeping “the basics of any good runner game: run, duck and jump” (Google blog, 2018). Spelunky's Derek Yu: ship one sloppy, fun little game fast, then a slightly bigger one (GameMaker, 2024).

Choose a scope you can finish by day 15.

How to check:

Backpack: 4–6 minutes of play, at most 10 evenings
“Scope” in GAME.md is all numbers
Open world, online play and such: in “Not in the game”

If extra features remain, ask: “Remove everything from Scope that is not on my list.”

Write two rules you can check

Put two rules in GAME.md to help judge later changes. For each, describe the experience you want and a sign that it has broken down. When you are unsure about an addition, come back to those rules and see whether it fits.

“The game is fun and pretty”

“The player feels every pit is doable first try without rushing; broken if they fall three times running”

Sort the cards: which statements can you check in the game, and which are still wishes?

The game is fun

The jump responds at once; broken if it lags the press

The graphics are pretty

The player sees enemies coming; broken if damage comes from off-screen

You want to keep playing

The farm doesn't punish; broken if crops die while you're away

Read both rules in GAME.md. Each needs a “broken if” condition. Then reply to the agent:

Approved.

Be bolder: suggest one unexpected detail in the rules, leave the rest alone.

Change one thing: [what].

Build your first draft

The agent now has enough to make a first draft: one screen of shapes, a main action, an obstacle, a win and a loss. First, see whether you enjoy jumping, shooting or planting, whichever matters in your game. We will work on pictures later.

The “Model to match” draft is flat for now too. We will add depth next lesson.

Make a draft of my game from GAME.md in sketch.html: one screen, one file, no libraries or images, shapes on a canvas. The draft has only the main action, one obstacle, a win and a loss. A round lasts up to 60 seconds. Top-down view, or side view for a platformer: depth comes tomorrow. All numbers go in CONFIG with plain-English comments. Controls: keyboard and mouse, or touch. Open sketch.html and tell me how to play and what to check first.

The agent opens the draft itself. Click the path to sketch.html in the chat, and the draft opens in the Browser panel. Open the draft in the built-in browser or by double-clicking the file. If the draft doesn't open by itself, double-click sketch.html. Play three rounds.

Optional: reuse your practice settings

Use this only if you want to keep the old jump or flight settings. For a different mechanic, start with new settings.

If my game has a jump or flight: read CONFIG in ~/games/first-game/remix.html, my numbers from day 3 are there. Use the jump and fall numbers as starting values for sketch.html. Don't change anything in first-game.

Mini Metro began the same way: a weekend prototype at Ludum Dare 26, rule “Nothing art-heavy” (postmortem, 2016). The first Super Mario Bros. prototype was a square moving around (Iwata Asks).

Open the draft and try the action you built the idea around.

How to check:

The main action works on first press
A round ends in a win or loss
After round three you want a fourth. If not, note why for tomorrow

If it is too hard, ask to make the first 20 seconds twice as easy. If the agent built the wrong action, say, “The main action is [action]. Change only that.”

Check and save the first version

The draft runs. Compare it with your idea before saving.

The agent checks

Check sketch.html: it opens without errors, a round ends in a win or a loss, all numbers are in CONFIG. Tell me what from GAME.md isn't in the draft yet. Don't change the code.

★ Fresh eyes

Start a new chat: type /cleartype /newopen a new session in the same folder. Have the agent check the files without the interview conversation.

Read GAME.md and sketch.html. Retell the game in one sentence. Don't change the code.

Compare the result with the one-line description in GAME.md.

You play

Play three rounds. Can you recognize the game you wanted to make?

Now ask to save the result. The agent will set up version history in the new folder:

Set up version history in this folder and save: “day 4: draft”. Add the tag day-04.

GAME.md says, “The game should be fun.” How could you make this more useful?

Add a condition you can checkYes. Describe what should happen in a particular section and what result would reveal a problem.
Leave it as it is; it is the main ruleIt is a useful wish, but it does not yet say what to check.
Change it to “very fun”That adds emphasis, but still no test. You need a specific condition.

The backpack cannot fit both an open world and online play. What should happen to those ideas?

Keep them; the agent will manageEven with an agent, a large project will not fit into ten evenings.
Remove the levels to make roomStart by removing the large extras your intended playthrough does not need.
Move both to “Not in the game”Right. That makes the limit clear to both you and the agent.

Why build the first draft from shapes?

The agent cannot work with picturesIt can, but we are leaving the look until days 7–8. Today we are checking the action.
To test the main action before working on artYes. First, find out whether you want to play it.
Only to make it load fasterThe main purpose is to check the action and rules while the draft is small.

You do not yet know how long the game should be. How can you continue?

Take the recommendation and record itYes. You can start there and revise it later.
Put the whole interview off until tomorrowIf you want to keep going, try the suggested option. You are still allowed to change your mind.
Skip the answer and let the agent decide silentlyIt is better to see and record the choice, so you know what was decided.

What can the Chrome dino example suggest for your first game?

Good games have lots of actionsThree are enough for the dino, and millions play it.
The dino is just a filler gameIt's a real little game. And it runs on three actions.
Choose a few actions and tune them wellYes. A smaller set leaves more time to work on each action.

Until which step can you switch art methods without moving the project over?

Only today, while on day 4You have some slack: until the project step on day 5.
Until day 5's project stepYes. That's where the game starts being built for your route.
Any time, it doesn't matterIt does: from day 5 the game is built for your route, and switching is extra work.

homework · day 4

Ask someone else to explain the game

must do

Give the draft to someone who has not seen it. Watch how they start playing
Then ask them to describe the game in one sentence
Compare that with the one-line description in GAME.md. If it is inaccurate, update it: “Change the one-line description in GAME.md to: …”

extra credit

A bolder second draft: play both, keep the closer one

Make a second draft in sketch-2.html: the same game, but with a bolder main action and one unexpected turn. Don't touch sketch.html. Open sketch-2.html and tell me what changed.

for your genre

Play a reference game for 10 minutes. Write down one specific design choice you want to try.

Celeste or Super Mario Bros.: how the first screen teaches jumping without words.

Vampire Survivors or Brotato: what the player is offered between waves.

Baba Is You or 2048: how the first level explains the rule.

Slay the Spire or Balatro: what the starting deck is made of and when a new card arrives.

Warcraft III or Age of Empires: what the player does in the first minute.

Stardew Valley or Cookie Clicker: what the player does on the first in-game day.

Reigns or Papers, Please: which choice comes up most often.

DOOM or Half-Life: how the first room teaches you to move and shoot.

Pokémon or Undertale: how the very first fight works.

how to tell it worked

criteria	pass
Draft	main action, win and loss work
GAME.md	8 decisions, at most three “agent's call”
One line	the player retold it almost in your words
Day's version	saved with the tag day-04

Time: about 20 minutes.

remember

Discuss the decisions with the agent. If you give it only one sentence, it will have to choose the rest.
Keep GAME.md to one screen. Eight decisions, with no more than three left to the agent.
A rule needs a check. Describe the intended player experience and a “broken if” condition.
Plan for about 5 minutes of play and 10 evenings of work. Put the other ideas in “Not in the game”.
Test the action with shapes first. Add pictures later.

Sources

Road to the IGF: Hempuli Oy's Baba Is You Joel Couture, Game Developer, 2018-02-15 · checked 2026-10-26
Road to the IGF: Lucas Pope's Papers, Please Leigh Alexander, Game Developer, 2014-02-04 · checked 2026-10-26
As the Chrome dino runs, we caught up with the Googlers who built it Google, 2018-09-06 · checked 2026-10-26
Derek Yu: an interview for GameMaker's 25th anniversary Ross Manthorp, GameMaker, 2024-11-28 · checked 2026-10-26
Postmortem: Dinosaur Polo Club's Mini Metro Robert Curry, Peter Curry, Game Developer, 2016-06-15 · checked 2026-10-26
Iwata Asks: Super Mario Bros. 25th Anniversary, Vol. 5 Nintendo · checked 2026-10-26
Guilty Gear Xrd Art Talk at Game Developers Conference 2015 Arc System Works · checked 2026-10-27
Codex: Pricing, ChatGPT: Pricing, Sora OpenAI: ChatGPT Plus is $20 a month; the Sora product has been unavailable since 2026-04-26 · checked 2026-10-27
ComfyUI: MiniMax H3, ComfyUI: Qwen-Image-Edit-2511 open models on your own NVIDIA card, model file sizes · checked 2026-10-30
OpenRouter: Pricing; model prices for FLUX 3 Image Klein, Nano Banana 2.1, GPT Image 2, Seedance 2.0 Mini the whole-game estimate is the course's own math from these prices. First top-up from $10: OpenRouter's payment form · checked 2026-10-27

You have finished the first world and have a game of your own, still made from shapes. Next lesson, we will move it into a project, make it fit the window and teach the agent to check screenshots.