Carrier

First-Person Gate Array

A first-person shooter built entirely out of digital logic on a small FPGA board. There is no processor anywhere in the design: no soft CPU in the FPGA and no microcontroller on the side. The 3D renderer, the monsters, the game rules, the keyboard and mouse interface and the sound are all state machines and memories written in VHDL.

What the game is

You walk through a textured 3D maze, open doors, pick up keys, health, ammo and weapons, and fight monsters that see you, chase you and shoot back. There are three levels, the last one ending with a boss. Later levels have rooms with different floor and ceiling heights, steps, ramps and pits, flickering and glowing lights, outdoor areas with a sky, and animated slime walls. Firing a gun makes noise that wakes up monsters in nearby rooms, unless they are set to lie in ambush.

The screen also shows a status bar, a minimap and a full-screen automap, along with title, briefing and score screens. Sound effects and music play in stereo.

How it runs

• Board: Digilent Cmod A7-35T (a Xilinx Artix-7 FPGA with 512 KB of external SRAM and 4 MB of flash).
• Video: 320x240 pixels, each drawn as a 2x2 block on a standard 640x480, 60 Hz VGA monitor through a Digilent Pmod VGA. Colors come from a 256-entry palette.
• Input: a PS/2 keyboard and a PS/2 mouse through two Digilent Pmod PS2 boards.
• Sound: stereo through a Digilent Pmod I2S2 to headphones.
• Boot: the design and all game data load from the board's flash at power-up, so no PC is needed.

The modules plug into a small custom carrier PCB. Inside the FPGA, the main blocks are:

Two frames are kept in SRAM: the game draws the next frame into one while the monitor shows the other. A frame takes about 3 to 6 ms to draw out of the 16.7 ms available at 60 Hz.

Controls

Development stages

The design was built in stages, each ending in a working bitstream, and comments in the code refer to them:

How it was checked

A Python model of the whole game (in tools/model/) is the reference. It generates the textures, levels and sounds, and it produces "golden" outputs: whole frames, game states and audio samples. Every hardware block has a self-checking simulation testbench that compares its output with the model, pixel for pixel and bit for bit. The largest test boots the complete design from a simulated flash chip and plays a scripted session.

Repository layout

Building

You need Vivado 2025.1 (its simulator, xsim, runs the testbenches) and Python 3.9 or newer. The Python tools use only the standard library, so building and simulating need no packages. The one exception is the UART debug tool (tools/uart/debug_uart.py), which needs pyserial. Either install it with pip install -r requirements.txt, or, if you use uv, run that script as uv run tools/uart/debug_uart.py ... and uv fetches pyserial by itself. Run everything from the repository root.

On a fresh clone, run the first two steps before anything else. They write the art, level and game-data files into build/, which the testbenches and the flash image read.

The build writes build/shooter_top/shooter_top.bit (to load straight into the FPGA) and shooter_top.mcs (to program into flash, so the game boots on its own). Two smaller designs build the same way: bringup_top shows test pages for checking the board and its wiring, and game_top is the first playable maze.

Art and sound

All textures, sprites, sounds and music are original, generated by the Python scripts in tools/model/. No assets from other games are used.