Dark Planet — DOS Game (1998) · Windows Port

Originally released in 1998. Reverse-engineered and ported to Delphi VCL in 2026.

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What is this

Dark Planet is a DOS side-scrolling action game originally written in Turbo Pascal using BGI256 graphics. This repository contains a full Windows port — not a wrapper, not an emulator, but a clean rewrite in Delphi VCL that runs natively on modern Windows.

Original game: Alexander Friz (@alexfrize · LinkedIn) All graphics and sprites: Ilia Kusmin (@rm3g25 · LinkedIn) Windows port: Ilia Kusmin

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Why this is engineering, not just a port

The original code used DOS-specific techniques that have no direct equivalent in Windows:

1. Banker's rounding killed the enemies Turbo Pascal Round(2.5) = 3. Delphi Round(2.5) = 2. One digit difference — enemies walked straight through walls into the sky. Fix: replaced Round() with Trunc(x + 0.5) to match original half-up behavior.

2. Off-by-one shifted every sprite Delphi open array parameters are always 0-indexed, regardless of the caller's array bounds. The entire sprite list was shifted by -1: earth tiles appeared in the sky, enemies showed wrong animation frames. Fix: N := 0 instead of N := 1 in the file parser. One character. Hours of debugging.

3. XOR rendering made corpses disappear DOS trick: draw a sprite twice with XOR = erase it. No memory needed, no cleanup. Windows double buffering clears the canvas every frame — corpses vanished instantly. Fix: full double-buffer architecture: FBack (static tiles) + FBuf (composited frame) → StretchBlt.

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What was rewritten

Original (Turbo Pascal / DOS)	Port (Delphi VCL / Windows)
PutImage / GetImage (BGI256)	TBitmap + BlitSprite with index-0 transparency
XORPut rendering	Double buffer: FBack + FBuf
Direct $A000 VGA memory	StretchBlt with 2x scale
Global variables	TForm1 class fields
Repeat…Until KeyPressed game loop	TTimer at 30ms
Delay() animation	Frame counter per sprite
DOS file I/O (Assign, Reset)	TFileStream

The core game logic — collision formulas, enemy AI boundaries, animation state machine — is preserved exactly from the original.

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What was improved

• Parabolic jump physics — replaced linear pixel-per-tick with velocity + gravity (FVelY += 0.55 per tick)
• Shoot while jumping — with correct frozen-Y hit detection at the moment of firing
• Alt+Enter fullscreen — scales to any resolution while preserving 320×200 aspect ratio with letterboxing
• Title screen — CDRAGON.PIC with fade-in text, matches original intro feel

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Controls

Key	Action
→	Move right
←	Move left
↑	Jump
Space	Shoot (works mid-air)
Alt+Enter	Toggle fullscreen
Esc	Quit

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How to run

1. Download the latest release zip from Releases
2. Extract anywhere
3. Run DPport.exe

No installation, no dependencies. Single folder, runs on any Windows.

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How to build from source

Requirements: Delphi 12 or newer (Community Edition works)

1. Clone the repository
2. Open src/DPport.dpr
3. Build (Ctrl+F9) — exe compiles to the project root next to the game assets
4. Run

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Repository structure

dark-planet/
  src/
    DPport.dpr
    DPport.dproj
    GameMain.pas
    GameMain.dfm
  SPRITES.NEW/
    *.IMG          -- all game sprites (graphics by Ilia Kusmin)
  LEVEL1.SF!       -- level 1 scenario
  LEVEL1.ITM       -- tile list
  LEVEL1.STF       -- enemy sprite list
  LEVEL2.SF!       -- level 2 scenario
  CDRAGON.PIC      -- title screen image
  README.md
  .gitignore

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About the original

Dark Planet was developed in 1998 using Turbo Pascal 7 with BGI256 graphics library. The game ran in DOS VGA Mode 13h (320×200, 256 colors). All sprites were drawn pixel-by-pixel using a custom DOS sprite editor — keyboard-only, no mouse.

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Port developed by Ilia Kusmin · iliakuzmin.dev