Family 4 — Input · rung 4.2

The rung that turns a demo into a game: read the D-pad every frame and move a sprite with it. This is the difference between watching and playing — the player is now in control.

Screenshot

What you'll learn

padHeld(0) returns a 16-bit bitmask of the buttons held this frame. The NMI reads the pad automatically every VBlank; you just read the result.
Test the D-pad bits (KEY_UP / KEY_DOWN / KEY_LEFT / KEY_RIGHT) and nudge the sprite's position each frame.
oamSetXY(id, x, y) updates only a sprite's position, leaving its tile and size untouched — the per-frame call you want inside a game loop (vs. oamSet, which rewrites the whole entry).

SNES concepts

This reuses the entire simple_sprite setup — tiles to VRAM, palette to CGRAM 128, OBJSEL — and adds a single new thing: the input loop. Sprite position is 9-bit X and 8-bit Y, so if you walk off an edge the coordinate wraps around. That OAM coordinate quirk is visible here for free; real games park an off-screen sprite at a hidden Y instead of letting it wrap.

How to build

make -C examples/input/move_sprite

Run move_sprite.sfc in luna and steer the sprite with the D-pad.

Modules used

console, dma, sprite, input

Ladder

← 4.1 controller · → 4.3 two_players