Architecture Overview

Free Eggbert's architecture closely mirrors the original Win32/DirectX 3 game structure, reconstructed from binary analysis. The codebase is structured as a set of cooperating C++ classes managed through a classic Win32 application model.

Layered Architecture

┌──────────────────────────────────────┐
│       Game Logic (C++20)             │
│  blupi.cpp / CDecor / CEvent / …     │
├──────────────────────────────────────┤
│  Free API  (Win32 → cross-platform)  │
│  Free Direct (DirectX → SDL3)        │
├──────────────────────────────────────┤
│  SDL3 / SDL_image / SDL_mixer        │
└──────────────────────────────────────┘

Game code only includes WinAPI-like and DirectX-like compatibility headers (windows.h, ddraw.h, dsound.h, etc.). SDL is never included directly by game source files.

Main Entry Point

Source file: src/blupi.cpp
Entry function: WinMain() (Win32-style)

blupi.cpp contains the application bootstrap, window creation, message loop, and top-level object instantiation.

Initialization Sequence

1. Create the application window
2. Instantiate CPixmap — DirectDraw surface manager
3. Call CPixmap::Create() — initialize display surfaces
4. Call CPixmap::CacheAll(TRUE, …) — load all image assets
5. Instantiate CSound — audio system
6. Instantiate CNetwork — DirectPlay (fails silently in most configs)
7. Instantiate CDecor — game world and logic engine
8. Instantiate CEvent — input handler and game phase dispatcher
9. Start multimedia timer for game tick updates
10. Enter the main message loop

Main Game Loop

The application uses a classic Win32 message loop with a multimedia timer:

// WinMain (blupi.cpp) — simplified
g_updateTimer = timeSetEvent(g_timerInterval, g_timerInterval / 4,
                             TimerStep, NULL, TIME_PERIODIC);

while (TRUE) {
    if (PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE)) {
        if (!GetMessage(&msg, NULL, 0, 0))
            return msg.wParam;
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    } else {
        if (!g_bActive) WaitMessage();
    }
}

The timer callback posts update messages. The window procedure handles WM_UPDATE by calling:

UpdateFrame();
SetDecor();
g_pPixmap->Display();

Core Classes

CDecor Source File Decomposition

CDecor is the most important class. Its implementation is split across 8 source files by responsibility:

World Grid System

The game world is a 100×100 grid of cells. Each cell stores a sprite index into the background/decor spritesheet.

• Grid dimensions: MAXCELX × MAXCELY = 100×100
• Object sprites: 64×64 px (DIMOBJX, DIMOBJY)
• Player sprites: 60×60 px (DIMBLUPIX, DIMBLUPIY)
• Explosion sprites: 128×128 px (DIMEXPLOX, DIMEXPLOY)

Render Channel System

CPixmap manages 15 independent DirectDraw surfaces, each identified by a channel constant. Layers are composited in order to build the final frame:

See Image Channels for the full reference.

Game Phase System

Game state is controlled by game phases, dispatched as Windows messages (WM_USER + N) and handled by CEvent. Examples:

• WM_PHASE_INIT — startup initialization
• WM_PHASE_PLAY — normal gameplay
• WM_PHASE_WIN / WM_PHASE_LOST — end of level
• WM_PHASE_SETUP — settings screen
• WM_PHASE_BUILD — level editor
• WM_PHASE_SERVICE / SESSION / MULTI — multiplayer lobby

See Game Phases Reference for all 60+ phases.

Moving Object System

Up to 200 moving objects (MAXMOVEOBJECT) can be active simultaneously. They are tracked in a fixed-size MoveObject[200] array within CDecor. Each object has a type (TYPE_*), position, animation state, and motion trajectory.

Object types include enemies (fish, bird, wasp), vehicles, bombs, collectibles, and visual effects. See Object Types.

Player State

Unlike the Planet Blupi engine which uses a Blupi[100] array, Free Eggbert stores the player state as individual member fields directly in CDecor (m_blupiPos, m_blupiAction, m_blupiDir, etc.).

In multiplayer, up to 4 players are tracked via network packets.

Audio Architecture

Audio is managed by CSound with two selectable backends controlled by the _BASS compile flag:

• Default (_BASS=FALSE): src/sound.cpp — DirectSound/MCI path
• BASS library (_BASS=TRUE): src/soundbass.cpp — BASS + BASSMIDI

See Audio System for full documentation.