This repository contains my Computer Organization and Assembly Language (COAL) project from Fall 2019. The project was implemented in MASM and run using DOSBox. It is based on the course requirement to create a menu-based side-scroller game inspired by the offline Chrome T-Rex game.
The project makes heavy use of pixel art sprites stored in static arrays in memory and rendered using low-level VGA routines.
│── src/
│ ├── file.asm # Main MASM source code
│ ├── fileins.txt # Instructions text file
│ └── FILES.TXT # Game resource list
│
│── static/
│ ├── ArrayPixelArt.PNG
│ ├── ArrayPixelPrint.PNG
│ ├── PhotoshopCharacterPixelArt.PNG
│ ├── PhotoshopMainMenu.PNG
│ ├── ShrinkedvsNormalArray.PNG
│ ├── vgapalette.png
│ ├── demo_VP8.webm
│ └── COAL-Project2019.pdf
The project fulfilled all base requirements from the assignment
- Menu-based navigation (Play, Instructions, Exit)
- Instructions loaded dynamically from a text file (
fileins.txt) - Game interface with multiple hurdles (aerial and terrestrial)
- Player movement in four directions: forward, backward, jump, bend
- Lives represented as heart sprites
- Display of top 3 highest scores with timestamp logging
- Randomly spawning hurdles and rare extra-life drops
- Level-up mechanism based on increasing score
All 2D sprites and characters were stored as static arrays in assembly memory.
Since MASM supported only 16 VGA colors, I converted colored images to fit this limited palette. This was done using a mix of Python scripts and Photoshop, although the original Python code was lost.
– reference VGA palette used.
I designed custom pixel fonts to display menu text like “PLAY”, “INSTRUCTION”, and “EXIT”.
– design of custom characters in pixel format.
Menu layouts were first designed in Photoshop and then mapped into the assembly coordinate system using the canvas grid as reference.
– final design reference.
One of the biggest challenges was MASM’s 40 KB stack limit. Sprites and fonts quickly exceeded this limit since each color value was stored in 1 byte, even though only 4 bits (16 colors) were actually needed.
Solution:
- I wrote a C++ utility to bit-pack sprite data, storing two color values per byte.
- On game execution, the data was decompressed back into full color arrays for rendering.
- This enabled me to include:
- Full font set
- 4 animated Sonic sprites
- Bomb, Pokémon, Tank, Angry Bird, and Cloud sprites
- Result: Less memory usage without losing quality.
– comparison of normal vs compressed arrays. Notice how the optimized version is visibly denser (shrunk horizontally).
You can watch the demo video below:
(click to play, recorded on DOSBox at high clockspeed)
Note: The jitter in sprites is due to the scanline rendering method. Each frame redraws the background before rendering the next sprite frame, which appears jumpy at higher DOSBox cycles.
- MASM615
- DOSBox (recommended cycles ~650,000 for smoother gameplay)
- Photoshop for sprite/menu design
- C++ utility for sprite compression
- Python (lost script) for color palette conversion
This was a solo project submitted as part of the COAL course (Fall 2019). All the designs and code was done by me.