MAINLINE

MAINLINE is a roguelike first-person shooter in which the player takes the role of caffeine injected into the arm of an exhausted person. The aim is to travel through the bloodstream and reach the brain before being metabolised, waking the host before they fall asleep. The player has a survival time of four seconds. Killing enemies adds time, while taking damage removes it. There is no on-screen timer; instead, the screen darkens and the heartbeat sound speeds up as time runs low.

Movement through the vessel is constant and forward-only, with the player strafing around the vessel wall to avoid enemy fire and clots. Each kill increases movement speed, and these increases stack, widening the field of view as speed rises. The speedometer is measured in nanometres. Every enemy has an internal weak point, and killing one through this point fully refills the player’s magazine. After each stage, the player chooses one of three cards to either swap their single weapon or upgrade its magazine size, damage, fire rate or reload. Upgrades carry over when switching guns. Dying returns the player to the start of the chapter with all upgrades and weapons removed.

The game has six chapters set in the peripheral vein, heart, lung, aorta, blood-brain barrier and brain, each with a distinct colour palette. Obstacles include adenosine receptors, platelet walls that block shots and sweeping clot lasers, and each chapter ends with a mutant boss. There are four modes: Normal Stages, EX1, EX2 and Endless, with Endless results recorded on Steam leaderboards. Expected playtime is one to three hours. The developer permits monetised streaming and videos. The game contains heavy use of flashing lights, strobing and sudden colour inversion, and players with photosensitive epilepsy are advised to take care.