Chrome Horizon demo pushes the Commodore 64 with a shooter written in C

A new demo called Chrome Horizon is demonstrating that it’s possible to create a fast shooter for the Commodore 64 using the C programming language instead of traditional assembly. The project focuses on showing how modern development tools can be used to build performance-heavy software for the classic system while still maintaining smooth gameplay. The demo was developed by programmer Stefano Coppi and is mainly intended as a technical showcase. For decades, most high-performance C64 games have been written in assembly because the hardware has strict limitations, including limited memory and a fixed number of hardware sprites. Assembly allows programmers to control the system at a very low level, which is why it has traditionally been seen as the only practical option for fast-paced games.

Chrome Horizon takes a different approach by using the Oscar64 compiler, a modern C compiler designed specifically for the Commodore 64. This tool allows developers to write code in C while still producing optimized machine code that runs efficiently on the system’s 6510 processor. The idea is to make development more accessible without sacrificing the performance required for action games. Even though the game engine is written in C, the demo still uses several advanced techniques commonly associated with assembly-based development. The game features smooth horizontal scrolling, multiple enemies on screen at once, and sprite multiplexing using raster interrupts. This technique allows the program to reuse hardware sprites in different parts of the screen, effectively displaying more objects than the system’s normal eight-sprite limit.

The gameplay itself follows the familiar formula of a side-scrolling shooter. Players control a spacecraft moving through a horizontally scrolling level while facing waves of enemy ships and projectiles. The currently available version only includes a short demo stage that highlights the engine and its technical capabilities rather than presenting a full game. At this stage, Chrome Horizon is primarily a proof-of-concept project. The demo is meant to show what can be achieved with modern C64 development tools and how C can be used effectively on the platform. The project is also connected to an upcoming book titled “Modern Code, Classic Steel: Engineering Professional Action Games for the C64.” The book will explain the techniques used during development and explore how modern programming workflows can be applied when creating games for classic hardware.

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