The N64 just got a seamless open world game

Homebrew developer James Lambert and Team Ultrarare have released Junkrunner 64, a fully playable open-world game for the Nintendo 64 that streams a massive environment without loading screens. The project was built for the N64brew 2025 game jam and is available to download now.

Lambert built a custom engine from scratch to handle a map scale comparable to modern open-world titles, all running on original 1996 silicon. He collaborated with developers Pyroxene, Caitlin G Cooke, terzdesign, and Kælin to produce the final game. The team built a sprawling landscape designed specifically for high-speed hoverboard traversal.

I think this is amazing. I would have loved to have a truly open world game back then. I am truly amazed by this creative programming. Watching the engine dynamically load geometry as the player speeds across the map is a technical marvel for a console that usually struggled with draw distances.

Streaming a massive map on 4MB of RAM

The Nintendo 64 is notoriously constrained by its hardware. The base console has only four megabytes of RAM and a tiny four-kilobyte texture cache. Most commercial games from the late nineties handled these limits by breaking worlds into small, discrete rooms. Games like Super Mario 64 used paintings as literal loading doors. The Legend of Zelda: Ocarina of Time hid its loading zones behind narrow corridors and heavy fog.

Lambert took a different approach for this project. His custom engine aggressively manages level-of-detail scaling and streams new environment chunks in the background while the player moves. The result is a seamless experience that never pauses to load the next area. The engine keeps track of the player's position and swaps low-poly distant geometry for high-resolution models as they get closer.

The game itself is built around this technical achievement. Players ride a fast-moving hoverboard. This forces the engine to load assets quickly to keep up with the camera. It is a direct stress test of the streaming system. The fact that it works flawlessly on real hardware is a massive leap forward for retro homebrew.

Life after Portal 64

Lambert is no stranger to pushing Nintendo's 64-bit machine past its supposed limits. He previously spent years developing Portal 64, a highly accurate demake of Valve's puzzle game that managed to get working portals running on the console. That project was voluntarily shut down in early 2024 after Valve expressed concerns about the use of proprietary Nintendo libraries.

Rather than stepping away from retro development, Lambert pivoted to original concepts. Junkrunner 64 proves that his technical skills extend beyond porting existing games. By building an original engine and collaborating with an independent team for art and music, he avoided the legal gray areas of his previous work. Pyroxene and Cooke provided the visual assets. The soundtrack was handled by beta dynast.

Playing it today

The N64brew game jam has historically produced some of the most impressive technical showcases for the console. It challenges developers to work within strict limitations over a period of a few months. Junkrunner 64 sets a new high bar for what the homebrew community can achieve. It is a complete, original game that does something commercial developers never managed during the console's retail lifespan.