Codex Prompt: Build the Cromonsters! Proof of Concept
You are the lead game designer and software engineer for Cromonsters!, an original comic monster-collecting RPG and AI coding experiment.
Inspect the existing repository before making changes. Preserve any useful conventions or existing work. If the repository is empty, scaffold the project using the default technical approach described below. Make sensible design decisions independently and proceed with implementation rather than stopping to request approval for minor choices.
Project Goal
In Programs\cromonsters, build a small but complete, locally playable proof of concept for Cromonsters!
The game should evoke the approachable scale, rhythm, and comic charm of late-1990s handheld monster-collecting RPGs, particularly the broad experience of the original Pokémon Red, Blue, and Yellow: top-down exploration, a small hometown, wild creature encounters, turn-based battles, collecting creatures, gaining levels, meeting a peer or rival, and setting out into the surrounding wilderness.
This is a spoof and affectionate genre homage, not a clone. All code, names, dialogue, maps, creatures, visual assets, music, terminology, combat details, lore, and interface designs must be original.
Do not copy or closely reproduce:
Pokémon characters, creature designs, names, dialogue, music, sound effects, sprites, maps, buildings, logos, fonts, menus, or story beats
The exact layout of Pallet Town or any Pokémon route
Poké Balls, the Pokédex, Professors, Gyms, Badges, Team Rocket, the standard Pokémon type chart, or equivalent terminology with only superficial renaming
Any proprietary assets or extracted game files
The proof of concept should feel familiar enough to function as parody while developing a clear identity of its own.
Intended Scope
Create a vertical slice, taking as much time as you need.
The playable world should contain:
One small starting settlement, comparable only in overall scope to an early-game hometown
Four surrounding wilderness areas
A short introductory sequence
Three starter choices
Wild Cromon encounters
Turn-based battles
A method for befriending, recruiting, or capturing wild Cromon using original terminology and mechanics
Experience and leveling
A small party and reserve system
A field journal or bestiary
A healing location
A basic supply system
At least one scripted battle against another human character
A simple field-trial objective that gives the demo a beginning, middle, and ending
A clear “Proof of Concept Complete” ending screen
Do not build a full campaign, multiple towns, a league, an eight-badge structure, online multiplayer, breeding, crafting, extensive evolution trees, or a procedural open world. Create clean foundations that can support those possibilities later.
Setting
The world should be a fictional, lightly fantastical region inspired by the Eastern Woodlands of North America, preferably in early autumn.
Base the environment on regional ecology and landscape:
Deciduous hardwood forest
Ferns, moss, fallen logs, mushrooms, and woodland streams
Meadows, goldenrod, asters, and migrating insects
Wetlands, ponds, marshes, and riverbanks
An estuary, tidal inlet, or fantastical waterway that allows marine Cromon to appear
Rural paths, wooden structures, field stations, and naturalist outposts
Create original names for the region, settlement, routes, landmarks, characters, items, and institutions.
Do not treat “Eastern Woodlands” as a generic Indigenous aesthetic. Avoid invented sacred traditions, faux tribal imagery, generalized “spirit animal” language, totem stereotypes, or a mixture of unrelated Native cultures. Let the ecological landscape provide the setting’s identity.
Several animals in the roster are not native to the Eastern Woodlands or Atlantic coast. Do not falsely imply that all thirty real animals naturally share one range. Handle distant species through an explicit fantasy device, research sanctuary, migratory phenomenon, unusual ocean current, visiting naturalist, rare event, or other internally consistent explanation. Their individual documentation should still identify their real-world ranges honestly.
The Initial Thirty Cromon
Create exactly one original Cromon based on each of the following animals:
Gray wolf
Moose
North American beaver
Eastern box turtle
Little brown bat
Great horned owl
Timber rattlesnake
Spotted salamander
Giant Pacific octopus
Moon jelly
Monarch butterfly
Luna moth
Seventeen-year cicada
Common green darner
Black-and-yellow garden spider
Green anole
American bullfrog
American alligator
Common loon
Broad-winged hawk
Ruby-throated hummingbird
Great blue heron
American bison
Humpback whale
Alligator gar
Manta ray
Atlantic horseshoe crab
American lobster
Lined seahorse
Ochre sea star
All thirty must exist in the game’s data model and field journal.
At least half should be available through ordinary exploration of the four initial wilderness areas. The remaining Cromon may be uncommon encounters, water-specific encounters, scripted sightings, sanctuary residents, unusual visitors, or creatures accessible through a clearly labeled developer showcase. Every Cromon must at least be viewable and battle-testable in the finished proof of concept.
Cromon Design Principles
Each Cromon should remain recognizably based on its real-world animal while receiving a memorable fantastical elaboration.
For every Cromon:
Invent an original, clever, pronounceable name
Base the name on the animal, its behavior, anatomy, habitat, sound, scientific terminology, or signature power
Avoid names already associated with major monster-collecting franchises
Avoid using the same naming formula thirty times
Do not merely attach an elemental suffix to the animal’s ordinary name
Preserve the animal’s characteristic silhouette and major anatomical features
Add one or two strong artistic flourishes rather than burying the animal under arbitrary armor, spikes, glowing eyes, and visual clutter
Derive its powers from real biology, behavior, ecology, or anatomy
Clearly distinguish real biological inspiration from fantasy extrapolation
Give it a distinct combat role, personality, habitat, strengths, limitations, and signature technique
Avoid making every large animal a slow tank and every flying animal a fast attacker
Keep the roster varied in shape, scale, temperament, strategy, and visual language
Examples of the desired reasoning include:
A beaver-inspired Cromon might manipulate terrain, redirect water, construct barriers, or repair structures
A bat-inspired Cromon might use echolocation, reflected attacks, darkness navigation, or sound-based perception
A salamander-inspired Cromon might possess limited regeneration or moisture-dependent recovery
An octopus-inspired Cromon might use camouflage, flexible positioning, decoys, ink, or multitasking
A cicada-inspired Cromon might combine long dormancy with sudden sonic force
A spider-inspired Cromon might control movement through webs, geometry, traps, or vibration sensing
A hummingbird-inspired Cromon might hover, accelerate rapidly, feed from flowers, or attack with precise bursts
A whale-inspired Cromon might communicate across great distances, manipulate pressure, sing, breach, or guide allies
These examples illustrate the approach. Do not simply copy them without further design thought.
Individual Cromon Documentation
Create one Markdown file for every Cromon.
Use a consistent directory and naming scheme, such as:
docs/cromon/001-cromon-name.md
docs/cromon/002-cromon-name.md
...
docs/cromon/030-cromon-name.md
Each file must contain:
Cromon Name
Real-World Inspiration
Name Origin and Wordplay
Real Biology and Ecology
Fantasy Elaboration
Visual Design
Silhouette and Identifying Features
Temperament and Behavior
Habitat in the Game
Affinity or Classification
Battle Role
Base Stats
Move Set
Signature Technique
Strengths and Weaknesses
Encounter Level and Rarity
Design Thought Process
Distinction Between Fact and Fiction
Future Art or Animation Notes
Also create a roster index at:
docs/cromon/README.md
The index should list all thirty Cromon, their source animals, affinities, habitats, and gameplay roles. Include a checklist or automated validation test proving that no required animal has been omitted or duplicated.
Starter Cromon
Choose three suitable starters from the thirty-animal roster.
The starters should:
Be visually and mechanically distinct
Be plausible companions for a beginning naturalist or traveler
Form an understandable three-way strategic relationship
Use an original relationship rather than simply reproducing the Fire-Water-Grass triangle
Remain useful throughout future development
Introduce different battle styles, such as defense, mobility, control, perception, construction, recovery, or precision
Document the starter-selection reasoning in:
docs/design/starters.md
World Structure
Design one original hometown and four connected wilderness areas.
The four areas should represent distinct ecological and gameplay spaces, such as:
A hardwood forest trail
A meadow, ridge, or old field
A wetland, pond, or river corridor
A tidal inlet, estuary, coastal reach, or fantastical far-current habitat
These are biome requirements, not mandatory names.
Each wilderness area should contain:
A distinct encounter table
Several low-level Cromon
At least one uncommon encounter
One small environmental interaction or traversal feature
One useful item or discovery
At least one sign, naturalist note, or NPC observation
A recognizable visual identity
A safe route back to town
Keep each area compact. The goal is a polished proof of concept, not a large but empty map.
Create:
docs/design/world.md
docs/design/encounter-tables.md
Core Gameplay
Implement a clear, fast turn-based battle system.
At minimum, battles should support:
Player and opponent Cromon
Health or vitality
Levels
Several meaningful stats
Turn order
Damage calculation
Accuracy or reliability
Affinities, strengths, and weaknesses
Status or field effects, kept intentionally limited
Switching party members
Wild-Cromon behavior
Recruitment, bonding, or capture attempts
Experience rewards
Level increases
Defeat and recovery
Readable battle messages
Simple opponent AI
Invent an original affinity system that reflects ecology, behavior, anatomy, or natural forces. Keep it small enough to understand in the proof of concept. Do not reproduce Pokémon’s type list or type chart with renamed labels.
Create a shared move library plus distinctive techniques for the Cromon. Every Cromon should have at least:
Two usable low-level techniques
A defined future move progression
One signature technique in its design documentation
Keep early battles brisk. A normal wild encounter should usually take only a few turns.
Original Terminology
Invent original terms for:
The creatures
The person who studies them
The player’s field journal
Recruitment or capture
The recruitment item or tool
Party and reserve storage
Healing
Affinities
Techniques or moves
Human opponents
The introductory field trial
Do not create terms that are merely “Poké” words with a different prefix.
The game may knowingly joke about genre conventions, but the humor should come from original writing rather than copied quotations or scenes.
Narrative Tone
Use a warm, lightly absurd, naturalist-adventure tone.
The writing may be self-aware about:
Why wild creatures agree to accompany children or amateur naturalists
The paperwork behind cataloguing dangerous magical wildlife
The impracticality of carrying enormous marine creatures
Local arguments over creature naming
Researchers treating astonishing monsters as routine fieldwork
The gap between heroic adventure and mundane ecological observation
Keep the humor affectionate rather than cynical. Do not turn every line into a joke. Give the setting enough sincerity that the creatures and landscape still feel worth caring about.
Visual Direction
Use an original retro pixel-art or crisp low-resolution aesthetic inspired broadly by classic handheld games, but do not copy Pokémon’s sprites, Game Boy palettes, interface layout, battle framing, tiles, fonts, or animation patterns.
Create:
Original environmental tiles or simple procedural equivalents
An original player sprite
Original NPC sprites
A recognizable portrait, battle sprite, SVG, or pixel-art placeholder for all thirty Cromon
Distinct silhouettes for the Cromon
Original interface elements
An original title treatment for Cromonsters!
The art does not need to be professionally polished. It must be coherent, readable, original, and easy to replace later.
Do not use copyrighted third-party art. If temporary assets are necessary, create them locally from original geometric shapes, programmatic drawings, or clearly labeled original placeholders.
Any sound effects or music must also be original. Simple synthesized tones are sufficient.
Technical Approach
If the repository does not already suggest a suitable stack, use:
TypeScript
Vite
Phaser 3
Vitest
ESLint and Prettier
Local browser storage for saves
Keep the game fully local. Do not require a backend, account system, API key, external database, or network connection after installation.
Structure the code so that:
Game rules are separate from rendering
Cromon, moves, items, encounters, dialogue, and maps are data-driven
Battle calculations can be unit tested without starting the game engine
Save data has a versioned schema
Future areas and Cromon can be added without rewriting core systems
Evolution can be added later even if it is not implemented now
Debugging tools do not leak into normal play
No single file becomes an unmanageable collection of unrelated logic
Include a developer showcase or debug menu that allows the developer to:
View every Cromon
Start a test battle with any Cromon
Adjust levels
Inspect base stats and techniques
Jump between maps
Reset save data
Controls and Accessibility
Support at least:
Arrow keys and WASD for movement
Enter or Space for interaction and confirmation
Escape for menus or cancellation
A visible controls screen
Keyboard-only play
Clear focus states and readable text
A mute control
Responsive scaling without blurry or distorted layouts
Avoid relying solely on color to communicate battle affinities, status effects, or warnings.
Proof-of-Concept Objective
Create a short introductory field assignment.
A suitable structure is:
The player begins in the starting settlement
A local naturalist, ranger, archivist, or similarly original character introduces Cromon
The player chooses one of three starters
The player receives a field journal and recruitment equipment
The player visits the four wilderness areas
The player records, battles, recruits, or observes a required number of Cromon
The player encounters one human peer or rival
The player returns to town
The field assignment is evaluated
The proof-of-concept completion screen appears
The exact details and terminology are yours to invent.
Documentation
Create or update:
README.md
docs/design/game-design.md
docs/design/world.md
docs/design/starters.md
docs/design/combat.md
docs/design/encounter-tables.md
docs/design/art-direction.md
docs/design/technical-architecture.md
docs/cromon/README.md
docs/cromon/001-*.md through 030-*.md
docs/roadmap.md
The main README should explain:
What the game is
Its parody and homage status
That it is not affiliated with Nintendo, Game Freak, Creatures, or The Pokémon Company
Installation
Development commands
Controls
Current features
Project structure
Testing
How to access the developer showcase
Known limitations
How to add another Cromon
How to add another wilderness area
Do not add an open-source license unless the repository already has one or the owner has explicitly requested one.
Testing and Quality Requirements
Add automated tests for at least:
Roster completeness
Unique Cromon identifiers
Unique Cromon names
Required source-animal coverage
Stat validation
Move references
Encounter-table validity
Damage calculation
Turn ordering
Affinity modifiers
Recruitment or capture calculations
Experience and leveling
Save and load serialization
Map-transition validity
Before finishing:
Install dependencies
Run formatting and linting
Run the test suite
Run the production build
Launch the game and test the main loop
Fix game-breaking errors and major console warnings
Verify that a new player can reach the completion screen
Verify that all thirty Cromon can be viewed and battle-tested
Do not leave the central gameplay loop as pseudocode, mock buttons, or unimplemented TODOs.
Scope Discipline
Prioritize, in order:
A working game loop
All thirty Cromon designs and documentation
Stable exploration and battles
A coherent starting town and four wilderness areas
Original visual placeholders
Polish and secondary effects
When a feature threatens the proof-of-concept schedule, implement the smallest maintainable version and document the fuller idea in the roadmap.
Working Method
Begin by inspecting the repository and summarizing its state.
Then:
Create a concise implementation plan
Establish the data model and project architecture
Define the thirty-Cromon roster
Implement the battle logic with tests
Implement exploration and encounters
Build the town and four wilderness areas
Add the introductory field trial
Add original placeholder art and interface elements
Write all Cromon documentation
Test the complete playthrough
Update the roadmap and README
Do not stop after writing the plan. Continue through implementation unless a genuine technical blocker makes further work impossible.
When uncertain, choose a reasonable original solution, document the choice, and proceed.
At the end, report:
What was implemented
The principal design decisions
Important files added or changed
Commands used to run the game
Test and build results
Known limitations
The most valuable next three development milestones