Catto

A lightweight, browser-based arena survival game where you control a cat fighting off waves of enemies. Built with vanilla JavaScript and HTML5 Canvas, featuring an upgrade system, multiple abilities, and progressive difficulty scaling.

🎮 Game Overview

Catto is a top-down survival game where you control a cat character defending against waves of increasingly difficult enemies. Collect experience points, level up, and choose from various ability upgrades to survive longer and achieve higher scores.

✨ Features

Core Gameplay

• Survival Mechanics: Fight off waves of enemies while managing health and resources
• Progressive Difficulty: Enemy strength and spawn rates increase over time
• Wave System: New enemy types unlock as you progress through waves
• Experience System: Gain XP from defeated enemies to level up

Abilities & Upgrades

• Claw Orbit: Rotating claws that deal continuous damage
• Whisker Whip: Forward-projecting whip attacks
• Hairball Burst: Random-direction projectile attacks
• Paw Slam: Area-of-effect ground slam attacks
• Cat Nap: Healing ability with temporary invulnerability

Enemy Types

• Street Rat: Fast, weak enemies (early game)
• Stray Dog: Medium health and damage (mid game)
• Cursed Crow: High health, threatening enemies (late game)

Technical Features

• Sprite-based Graphics: Custom cat, enemy, and ability sprites
• Responsive Controls: WASD and arrow key support
• High Score Persistence: Local storage for score tracking
• Smooth Animation: 60 FPS gameplay with requestAnimationFrame
• Fallback Rendering: Graceful degradation if sprites fail to load

🎯 Controls

• W / ↑: Move up
• S / ↓: Move down
• A / ←: Move left
• D / →: Move right
• Pause: Game automatically pauses during level-up selection

🚀 Installation & Setup

Prerequisites

• Modern web browser with HTML5 Canvas support
• No external dependencies or build tools required

Quick Start

1. Clone or download the project files
2. Open index.html in your web browser
3. Wait for sprites to load
4. Click "Start Game" to begin playing

File Structure

catto/
├── index.html          # Main HTML file with game UI
├── game.js            # Core game logic and mechanics
├── styles.css         # Game styling and UI layout
└── assets/            # Game sprites and images
    ├── neko.png       # Player cat sprite
    ├── dog.png        # Dog enemy sprite
    ├── crow.png       # Crow enemy sprite
    ├── rat.png        # Rat enemy sprite
    └── paw.png        # Claw/paw ability sprite

🎲 Gameplay Mechanics

Leveling System

• Gain XP by defeating enemies
• Level up to unlock ability upgrades
• Choose from 2 random upgrades per level
• XP requirements scale progressively

Difficulty Scaling

• Wave-based: New enemy types unlock every 25 seconds
• Level-based: Enemy stats increase with player level
• Time-based: Spawn rates and enemy caps increase over time
• Capped scaling: Maximum limits prevent impossible difficulty

Combat System

• Automatic abilities: Claw orbit and timed abilities activate automatically
• Manual positioning: Strategic movement to avoid enemy contact
• Invulnerability frames: Brief protection after taking damage
• Collision detection: Precise hitbox calculations for all entities

🛠️ Technical Implementation

Architecture

• Canvas-based rendering: 2D context for smooth graphics
• Entity-Component pattern: Separate arrays for different game object types
• State management: Centralized game state with immutable-like updates
• Event-driven input: Keyboard event listeners for responsive controls

Browser Compatibility

• Modern browsers: Chrome, Firefox, Safari, Edge
• Canvas support: Requires HTML5 Canvas API
• Local storage: High score persistence
• No polyfills: Pure vanilla JavaScript implementation

🎨 Customization

Modifying Game Balance

• Adjust enemy stats in enemyTypes object
• Modify ability scaling in abilities configuration
• Change XP requirements in levelUp() function
• Tune spawn rates in spawnEnemies() function

Adding New Content

• New abilities: Extend the abilities object
• New enemies: Add to enemyTypes and sprite loading
• New mechanics: Implement in game loop functions
• UI elements: Extend HTML and CSS as needed

🐛 Known Issues & Limitations

• Sprite dependency: Game requires all sprite files to be present
• Fixed resolution: Canvas size is hardcoded (1200x800)
• Local-only: No online multiplayer or cloud saves
• Mobile support: Designed for desktop keyboard input

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Enjoy playing Catto! 🐾

Survive as long as you can, level up your abilities, and beat your high score!