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Building a Monster Capture Game from Scratch

Every game developer who loves Pokemon has had the same thought: "I could build my own." And you can. The question is whether you should invest 12-18 months building engine systems, or spend that time making your game unique.

This page breaks down exactly what building a monster capture engine from scratch requires -- the systems, the timeline, the cost -- so you can make an informed decision.

The Systems You Need to Build​

A production-quality monster capture game requires these interconnected systems. Each one is deceptively complex.

Monster Data System (4-6 weeks)​

  • Species database with base stats, types, abilities, growth rates, catch rates, egg groups
  • Individual monster instances with IVs, EVs, nature, friendship, status conditions
  • Form variants (regional forms, mega evolutions, gender differences)
  • Monster storage (party of 6, PC boxes with search and sorting)
  • Serialization for all of the above

Battle System (8-12 weeks)​

This is where most from-scratch projects stall. A proper battle system needs:

  • Turn order calculation with speed tiers and priority moves
  • Damage formula with type effectiveness, STAB, critical hits, weather, terrain, abilities
  • 600+ moves with unique effects (stat changes, status conditions, multi-hit, recoil, drain, etc.)
  • Battle state machine (wild, trainer, PvP, double battles)
  • Item usage during battle
  • Capture mechanics with ball types and catch rate formulas
  • Switch-in/switch-out logic with entry hazards and abilities
  • AI that makes intelligent decisions (not just random move selection)
  • Battle UI with animations, health bars, move selection, and status indicators
  • Experience calculation and level-up flow

Evolution System (2-3 weeks)​

Not just "level 36 = evolves." Real evolution systems need:

  • Level-based, item-based, trade-based, friendship-based
  • Location-based, time-of-day-based, stat-based
  • Hold item evolution, move knowledge evolution
  • Evolution chains with branches
  • UI for evolution sequence with cancellation support

Overworld System (6-8 weeks)​

  • Grid-based tile movement with smooth interpolation
  • Collision detection on a tile grid
  • Multi-map transitions with spawn points
  • NPC pathfinding and scheduling
  • Special tiles: tall grass, water, bridges, ledges, slippery ice, waterfall climb
  • Encounter triggering with terrain-based tables
  • Day/night cycle with timed events
  • Player sprite with 4-direction animation

Event/Scripting System (4-6 weeks)​

  • Dialog system with portraits, choices, and variables
  • NPC interaction triggers
  • Conditional branching (badges, items, variables)
  • Cutscene playback (camera moves, character movement, fades)
  • Item giving, money transactions, monster gifting
  • Warp points and scene transitions
  • Shop system with buy/sell

Save System (2-3 weeks)​

  • Serialization of all game state (monsters, items, position, variables, quests)
  • Multiple save slots with metadata
  • Save versioning for backward compatibility
  • Auto-save with corruption protection

UI System (4-6 weeks)​

  • Battle HUD (HP bars, move selection, type indicators)
  • Monster menu with stats, moves, and ribbons
  • Bag with categorized items
  • Pokedex with seen/caught tracking
  • Shop interface
  • Settings menu
  • Dialog boxes with typewriter effect

Supporting Systems (3-4 weeks)​

  • Audio management (BGM, SFX, with crossfading)
  • Localization pipeline
  • Type chart editor
  • Quest/achievement system
  • Breeding and egg hatching

Total Estimate​

MetricFrom ScratchWith OpenMon
Development time12-18 months1-2 months
Cost (solo dev, opportunity)$50K-$100KSee website
Cost (hired team)$150K-$300KSee website + your game content
Lines of engine code80,000-120,0000 (provided)
Bug surface areaMassiveBattle-tested across projects
Multiplayer6-12 additional monthsToggle on (Online tier)

These estimates assume a developer who already knows Unity or Unreal well. Add 3-6 months if you are learning the engine simultaneously.

The Hidden Costs​

The systems list above covers the obvious work. Here is what catches people off guard:

Edge Cases​

Pokemon's battle system has hundreds of edge cases. What happens when a move hits a substitute? When Baton Pass transfers stat changes? When a Pokemon with Sturdy is hit by a multi-hit move? Each edge case is a research task, an implementation task, and a testing task.

Balance Testing​

With 18+ types and hundreds of moves, your type chart and damage formulas need extensive balancing. OpenMon ships with battle-tested formulas based on the Gen V+ damage model.

Platform Quirks​

Mobile touch input, WebGL memory limits, console certification requirements. Each platform has its own surprises. OpenMon handles cross-platform abstractions so you do not have to.

Maintenance Burden​

Every system you build is a system you maintain. Unity updates, platform SDK changes, and player bug reports compound over time. With OpenMon, engine maintenance is handled for you.

What You Should Build from Scratch​

Not everything should be off-the-shelf. Your game's unique identity comes from:

  • Your monsters. Original designs, lore, and world-building.
  • Your story. Characters, plot, dialog, and world events.
  • Your art style. Sprites, tilesets, UI themes, animations.
  • Your music. Soundtrack that sets your game apart.
  • Your unique mechanics. The twist that makes your game different from every other monster catcher.

These are the creative elements that no engine can provide. Spend your time here, not reimplementing damage formulas.

The OpenMon Approach​

OpenMon provides the complete engine foundation:

  • All the systems listed above, integrated and tested
  • 2,000+ automated tests covering battle mechanics, save/load, and monster data
  • ScriptableObject-based configuration -- no code required for content creation
  • Public SDK API for extending systems without modifying source
  • Full source code available (Source tier) if you need to go deeper

You focus on what makes your game yours. OpenMon handles the engineering.

Get Started​