moonshot

technical

gnista

a game engine, written in c0, running on moonshot

gnista is a game engine built from scratch in c0, running as a windowed ring-3 program on moonshot. the engine and moonshot are grown together, and every real limitation the engine hits becomes a fix in the kernel or the compiler. infecteria is the game built on it.

entities

an entity is a layout with a position, a size, a velocity, a kind and a few fields the game uses as it likes. entities live in a pool allocated once at startup, and their slots are reused. a wall is an ordinary entity that never moves, so one collision routine and one drawing routine cover everything.

drawing

nothing in gnista draws straight to the window. every frame is drawn into a buffer of its own and handed over in one present call, so a task switch can never show half a frame. the buffer is sized for the largest window the machine can hand out, so the game carries on when its window is resized. there are rectangles, circles, text in the kernel's font and a camera that follows the player.

movement is a fixed step per frame, so a busy system slows a game down instead of making it skip. animation runs on real time, so a sprite cycles its frames at the right rate whatever the scheduler is doing.

sprites

sprites are loaded at run time from the files pensel saves, so art drawn on the machine shows up in a game with no rebuild. a sprite file can hold several frames, and an animation clip is a run of them. a game carries fallback art for when nothing has been drawn yet.

scenes

a scene is a plain function that runs its own loop for as long as it is on screen and returns the scene to run next, or 0 to end the game.

a moonshot screen with an empty shell on the left and infecteria on the right. on a dark blue background the word infecteria is written in large green letters, a small green bacterium sits under it, and below are three lines of small text: arrows move, e absorb a cell, q make it a factory; outrun the red ones: only your factories can hurt them; space to start, esc to quit.
infecteria's title scene, drawn with gnista's own text in the kernel's font.

infecteria

in infecteria you are a bacterium. you infect cells and absorb them or turn them into factories, while antibacteria hunt you and heal the cells you left half infected. only your factories can hurt them. you win by taking every cell. a file called infecteria.seed holding a number fixes the world, so a layout worth replaying can be kept.