Family 5 (Game math & framework) · a capstone.

Why it matters for your game

Every example so far teaches one system. This one teaches the shape that holds them together: a title screen, a play loop with a goal and a clock, and a game-over screen that loops back. It's small enough to read in one sitting and fork as the starting point for your own game.

Screenshot

What you'll learn

The single idea: a game is a state machine around one frame loop. Every frame you WaitForVBlank(), read the pad, then switch (game_state) to the code for the screen you're on. A transition is just an assignment to game_state plus a one-time setup for the new screen:

TITLE --START--> PLAY --timer hits 0--> OVER --START--> TITLE

It recombines rungs you've climbed: input drives the arrow sprite, a second sprite is the coin, a bounding-box test scores it, text is the HUD, and rand()/srand() scatter the coin. Motion and collision are deliberately trivial — the lesson is the structure, not the mechanics.

When the enum + switch starts to sprawl in a bigger game, the opt-in scene framework is the next step up — see scene_stack.

What to observe / if it breaks

Correct run: title shows PRESS START; in play the D-pad moves the arrow, touching the coin bumps SCORE and respawns it, TIME counts down; at zero the game-over screen shows the final score; START plays again.
Nothing happens on START: input is read with padPressed (edge) — a held button fires once; that's intended for menu transitions.
Sprites invisible in play: setMainScreen(LAYER_BG1 | LAYER_OBJ) must enable OBJ, and colour 1 of an OBJ palette (CGRAM 128+) must be non-black.
Number smears (10 → 9 leaves 90): clear the field before reprinting — this example prints spaces over the old digits first.

Probe oracles: game_state (0 title / 1 play / 2 over), score, time_left.

Build & run

make

../../../tools/luna-test/bin/luna game_skeleton.sfc # luna-gui: tap START, steer with the D-pad

Modules used

console, dma, background, sprite, text, input

Where you are

The capstone of the basics family — it ties input, sprites, text and a state machine into a whole game. For the same structure via the scene framework, see scene_stack; for a HUD box, panel_hud.