Forge2D

2D platformer engine with integrated authoring tools. Built on SDL3, EnTT, and modern C++.

Forge2D includes a runtime engine, level editor, character creator, enemy designer, and tile animation tool. All game content is data-driven through JSON -- no hardcoded assets, no external editors required.

Features

Runtime

• Entity Component System (EnTT) with data-oriented, cache-friendly design
• Fixed 120 Hz physics with accumulator-based frame decoupling and interpolated rendering
• Multi-pass AABB collision with slope correction, step-up, and moving platform carry
• Combat system with sword hitbox sweeps, enemy stomps, dash, and invincibility frames
• Camera with deadzone follow, exponential smoothing, screen shake, and directional punch
• Multi-directional gravity (down/up/left/right) for wall-run levels
• Parallax scrolling backgrounds with per-layer scroll factors
• Dual-track audio engine with per-animation SFX, time-stretch, and background music

Authoring Tools

• Level editor with tile palette, multi-tool workflow, grid snap, undo, pan/zoom, and play-test
• Character creator with 8 animation slots, per-slot SFX, hitbox handles, and drag-and-drop sprites
• Enemy designer with configurable speed, health, animation states, and per-slot SFX
• Tile animation creator for building animated sequences from PNG folders
• Parallax background editor with adjustable scroll factors and infinite repeat

Quick Start

Prerequisites: vcpkg

# Install dependencies
vcpkg install sdl3 "sdl3-image[png]" sdl3-ttf sdl3-mixer entt nlohmann-json --triplet arm64-osx

# Build
cmake --preset mac-arm && cmake --build --preset mac-arm

# Run (from project root)
./build/forge2d

Available presets: linux, mac-arm, mac-intel, windows

Manual CMake

cmake -B build \
  -DCMAKE_TOOLCHAIN_FILE=~/tools/vcpkg/scripts/buildsystems/vcpkg.cmake \
  -DVCPKG_TARGET_TRIPLET=<your-triplet>
cmake --build build

Architecture

Forge2D uses an ECS architecture. Components are plain structs in Components.hpp. Systems are stateless free functions under include/systems/, one per file. No inheritance in the hot path.

The game loop uses a fixed timestep -- physics ticks at 120 Hz, rendering interpolates between frames via PrevTransform and an alpha factor.

Systems pipeline (per physics tick):

Input → Movement → Ladder → Bounds → PlatformTick → Collision
→ PlatformCarry → Floating → PlayerState → Animation → SFX → Camera

Scenes inherit from Scene and implement the standard lifecycle (Load, Update, Render, Unload). SceneManager owns the active scene and handles transitions.

The audio engine composes AudioDevice, SoundBank, and MusicPlayer behind an AudioEngine facade. Two independent playback tracks keep looping SFX (footsteps) from being interrupted by one-shot sounds (slash, hurt).

The level editor is decomposed into focused subsystems (EditorToolbar, EditorCanvasRenderer, EditorUIRenderer, EditorPalette, EditorPopups, EditorFileOps, EditorSurfaceCache). Tools inherit from EditorTool and operate through a decoupled EditorToolContext.

Source in src/, headers in include/. Engine-layer headers live in include/engine/ and have no knowledge of game-specific types. Game-layer headers in include/game/ depend on the engine, never the reverse.

Controls

Gameplay

Key	Action
A / D	Move
Space	Jump (hold for higher)
F	Slash
Double-tap A/D	Dash
Ctrl	Crouch
W / S	Climb (on ladder)
ESC	Pause
F1	Debug hitboxes

Gamepad supported (Xbox layout). Hot-plug enabled.

Level Editor

Key	Action
Arrow keys / Middle-drag	Pan
Scroll	Zoom
1-9	Switch tools
Delete	Remove selection
Ctrl+S	Save
Ctrl+Z	Undo

License

Copyright (c) 2025 Tanner Davison. All Rights Reserved.