Zero Sector is a free vertical-scrolling shoot 'em up game set in a distant future where an interstellar virus threatens the Milky Way. Players pilot a prototype starfighter, navigating through a starry backdrop while engaging in intense battles against viral entities. The game features a core loop where players progress through levels, earn resources by defeating enemies, and upgrade their fighter to face increasingly challenging stages. The automatic and manual control options enhance the gameplay experience, allowing players to dodge intricate bullet patterns and unleash powerful attacks.

The game offers an Endless Mode, providing players with an opportunity to survive in an infinitely generated starfield, testing their reaction skills and aiming for high scores. Players can upgrade their primary weapon by leveling up their bullets and increasing the fire rate, which is crucial for maximizing damage output. Victory is achieved by defeating a specified number of viruses, while failure occurs through collisions with enemy units or projectiles, adding a layer of challenge to the gameplay.