Using LLMs for Firmware Graphics Development: From Code Review to a Playable Game

In recent years, large language models have improved rapidly at code generation, program analysis, and fault localization. Firmware is a stricter test of engineering understanding than typical application development: operating-system services are incomplete, debugging is limited, and memory and protocol use are unforgiving. A bad pointer lifetime, struct definition, or protocol GUID can terminate the program immediately—often with no visual feedback.

A typical exercise is to have a coding assistant implement a simple Chinese Breakout-style game in firmware. The process is not “one prompt, ship it.” It goes through code review, compile checks, boot debugging, graphics fixes, and gameplay polish. The value is not which model wrote the game, but which stages of low-level development models actually help, and where developers still have to decide.

Why firmware games test models more rigorously

Desktop apps can rely on window systems, input frameworks, graphics libraries, and debuggers. Firmware often runs in a boot environment and must handle:

• discovering and initializing graphics output protocols
• obtaining a framebuffer and writing pixels
• reading keyboard events
• the main loop and timing
• memory allocation and data-structure lifetimes
• exit, reboot, and abnormal behavior
• compile targets, architecture, and how the firmware image is launched

“Compiles” does not mean “runs,” and “runs” does not mean “draws.” Validation has at least four layers:

1. Syntax and types: the source compiles.
2. Link and image: the boot image matches the target environment.
3. Boot path: the program reaches the entry point and main loop.
4. Runtime logic: display, input, collision, and exit behave as intended.

Models can draft code quickly, but they cannot replace a real runtime. Header versions, architecture, protocol implementations, and boot method all matter. Treat generated code as a candidate implementation, not a final answer.

Start with code review, not a rewrite

Given a multi-file project produced by other automation, do not ask the model to rewrite first. Have it build a system picture.

1. Map module responsibilities

Confirm how the entry module, game state, rendering, input, and shared data structures relate. Check whether:

• the entry function performs required initialization
• the main loop has a clear exit condition
• game logic depends on objects that are not yet initialized
• rendering assumes graphics output always exists
• input handles no input, repeat input, and quit
• modules have circular dependencies

The goal is a call graph, not immediate patches. Without module boundaries, local fixes hide design problems.

2. Then inspect resources and lifetimes

The most dangerous firmware bugs are lifetime bugs, not syntax errors. Examples:

• using a protocol information pointer after it is invalid
• using an old framebuffer description after a mode switch
• use-after-free
• allocating in a loop without freeing
• storing the address of a temporary in a long-lived struct
• assuming a service always exists without checking return status

Models can often flag these risks. Still require them to explain why it is dangerous, when it triggers, and how to verify the fix—not just accept a patch.

First run failure: why the program exits immediately

A program may build, print that the main loop started, then exit. Entry logic likely ran; later init or a protocol call failed.

Stage logs help:

[BOOT] entry reached
[VIDEO] locating graphics output
[VIDEO] protocol acquired
[VIDEO] querying current mode
[VIDEO] framebuffer prepared
[GAME] state initialized
[GAME] entering loop

Each line is an execution boundary. The last printed line narrows the fault.

Pay special attention to mode-query structures. Some firmware interfaces return objects owned by the system, valid only for a defined lifetime. Using an old pointer after a mode switch can mean:

• the memory was reallocated
• the struct no longer matches the current mode
• the framebuffer address changed
• later drawing hits invalid memory
• the program dies with little error output

Safer practice: after switching modes, re-query the current framebuffer info and check every protocol return status. The fix is not “add one more if”—it is respecting the lifetime of interface objects.

Second class of bugs: wrong protocol identifiers

If the program no longer crashes but shows nothing, distinguish:

• failure to obtain the graphics output protocol
• protocol obtained, but draw parameters or framebuffer use are wrong

Firmware locates protocols by globally unique identifiers. A wrong GUID, or mixing versions/purposes, often yields “protocol not found.” That may not crash. Typical symptoms:

• init returns failure
• black screen
• draw functions never run
• return to the boot menu
• logs show entry succeeded but no graphics

Debug layer by layer:

1. Was a graphics output service found?
2. Was a protocol instance obtained?
3. Was the current mode retrieved?
4. Are width, height, and pixel format valid?
5. Is the framebuffer address null?
6. Does drawing exceed the screen?
7. After writes, is the visible region actually updated?

Models are good at comparing call sequences, GUIDs, and error handling. Final proof still requires real firmware; simulators and devices often differ.

From “it displays” to “it plays”: engineering the game loop

Once graphics work, implement the game. A simple Breakout clone needs:

• paddle position and speed
• ball position, radius, and velocity
• brick grid
• ball vs. screen edges
• ball vs. paddle
• ball vs. bricks
• score, lives, and end state
• reset and restart

Split each frame into a fixed sequence:

read input
update player state
update ball position
handle edge collisions
handle paddle collisions
handle brick collisions
update game state
clear or redraw
print debug info

Order matters. Draw-then-update adds a frame of lag. Mixing collision and motion causes tunneling or double bounces.

Without high-level graphics libraries, draw with pixels or simple primitives. Implement rectangles, approximate circles, and text regions first; then color, borders, and animation. Correct state machine before visual polish.

Second-pass quality: maintainability, not only bugfixes

Round one: boot, display, input. Round two: engineering quality.

1. Avoid hardcoding

Centralize screen size, brick layout, colors, and initial speed so modes can change without scattering edits.

2. Bound checks

Guard coordinates against overflow, negatives, and screen edges. Clip rectangles before writing the framebuffer.

3. Pace the main loop

Firmware timers may be coarse. Too fast is unplayable; too slow stutters. Use a fixed timestep if a timer exists, or scale motion by measured frame delta.

4. Improve input

Distinguish press, release, and hold. Continuous hold is natural for left/right; quit and restart should not fire twice on one key.

5. Make errors observable

Ship with fewer on-screen logs, but keep development traces for init, protocol status, mode parameters, framebuffer validity, and state transitions. Logs should map to paths, not volume.

Where models actually help

Models are most useful for:

• reading unfamiliar projects quickly
• producing module maps and issue lists
• catching common API misuse
• hypothesizing faults from logs
• offering alternative fixes
• writing repetitive draw and update code
• turning scattered requirements into tasks

Limits remain:

• assuming interface behavior without checking the environment
• generating plausible code for the wrong firmware version
• missing pointer lifetimes and layout
• claiming a fix without a run
• breaking other modules while patching one bug

Reliable collaboration: the model proposes, the developer supplies evidence, the model iterates. Every change should come with compile results, boot logs, screen behavior, or a minimal repro. Without that loop, the model is only guessing statically.

A collaboration workflow for low-level work

1. Define the environment: architecture, boot method, graphics protocol, input.
2. Establish a baseline: compile, boot, and locate the first failure.
3. Static review: modules, lifetimes, error handling, call order.
4. Minimal fixes: one class of problem at a time; avoid wholesale rewrites.
5. Layered verification: boot, protocol, drawing, input, game logic.
6. Polish last: performance, structure, logs, and visuals after the game is stable.

That process is more useful than racing “which model writes faster.” Metrics should include time to first runnable build, localization speed, post-fix stability, maintainability, and fit to the real environment.

LLMs can already join fairly complex firmware work. Outcomes still depend on clear verification goals, careful logging, and a strict engineering loop. The skill worth learning is not getting a model to emit an entire program at once, but splitting a vague goal into observable, testable, iterable tasks.