main.c File Reference

Random number generation demo. More...

#include <snes.h>
#include <snes/text.h>
#include <snes/gameloop.h>

Functions
int	main (void)
	Entry point — gameLoopRun never returns.
static void	on_init (void)
	One-time setup. Static labels + first random + screen on.
static void	on_update (void)
	Per-frame: read input, regenerate on A, re-seed on B, print value.

Variables
u16	current_value
	Current random value to display.

Detailed Description

Random number generation demo.

Generates and displays random 16-bit numbers on button press. Demonstrates the LFSR-based pseudo-random number generator and how to seed it for varied sequences.

Every game needs randomness — enemy spawn positions, item drops, damage variance, shuffle order. The SNES has no hardware RNG, so we use a software PRNG seeded from the frame counter at game start.

Ported from PVSnesLib "random" example by alekmaul.

SNES Concepts

• rand() — 16-bit LFSR pseudo-random number generator
• srand() — seed the PRNG (use frame_count for unpredictable sequences)
• Text module for hex and decimal display
• padPressed() for single-press button detection

What to Observe

• Press any button to generate a new random number
• Both hex and decimal values are shown
• Press B to re-seed the PRNG from the frame counter
• After re-seeding, the sequence changes unpredictably

Modules Used

console, sprite, dma, background, text, input

See also

console.h (rand, srand)

Function Documentation

main()

int main

(

void

)

Entry point — gameLoopRun never returns.

on_init()

static void on_init ( void  )

static

One-time setup. Static labels + first random + screen on.

on_update()

static void on_update ( void  )

static

Per-frame: read input, regenerate on A, re-seed on B, print value.

The framework calls this once per VBlank — padPressed() reads the NMI-updated joypad buffer and returns only the bits that just transitioned (single-press detection), so holding the button down keeps producing the same number until release.

Variable Documentation

current_value

u16 current_value

Current random value to display.