Answer by Oka for GetRandomValue function in Raylib giving 0 every time

In your code, you are calling GetRandomValue without first calling SetRandomSeed.

void SetRandomSeed(unsigned int seed); // Set the seed for the random number generator

As of Raylib 5, there are two possible pRNGs: C's standard rand (srand), and rprand - an implementation of xoshiro128**.

If the standard C pRNG is in use, calling rand() without first calling srand(seed) behaves as though srand(1) was called during program startup. In this situation, it is extremely likely you would see non-zero values - but since the seed is always the same (1), they would be the same values on every execution of the program.

If rprand is in use, calling the internal rprand_xoshiro without first calling rprand_set_seed results in a pRNG with a zero-state: all numbers generated will be zero. I would hazard a guess that this is what is occurring on your system (in effect: when you call GetRandomValue before SetRandomSeed).

InitWindow calls

SetRandomSeed((unsigned int)time(NULL));

as the last thing it does, and is often the first Raylib library function called in an application, so you can simply reorder the code:

InitWindow(CELLSIZE * CELLCOUNT, CELLSIZE * CELLCOUNT, "retro snake");SetTargetFPS(60);Vector2 foodPos = {    GetRandomValue(0, CELLCOUNT - 1),    GetRandomValue(0, CELLCOUNT - 1)};

As pointed out by @pmacfarlane, your coordinates, which are in the range [0, CELLSIZE) must be multiplied by CELLSIZE for the rectangle to be drawn at the correct offset.

Additionally note that the first BeginDrawing(); (outside the loop) is erroneous.

A working example (press SPACE to move the rectangle to a random position):

#include <raylib.h>#define CELLSIZE 30#define CELLCOUNT 25#define RANDOM_CELL() (GetRandomValue(0, CELLCOUNT - 1))Color green = { 173, 204, 96, 255 };Color darkGreen = { 43, 51, 24, 255 };int main(void){    const int dim = CELLCOUNT * CELLSIZE;    InitWindow(dim, dim, "retro snake");    SetTargetFPS(60);    Vector2 foodPos = { RANDOM_CELL(), RANDOM_CELL() };    while (!WindowShouldClose()) {        if (IsKeyPressed(KEY_SPACE)) {            foodPos.x = RANDOM_CELL();            foodPos.y = RANDOM_CELL();        }        BeginDrawing();        ClearBackground(green);        DrawRectangle(foodPos.x * CELLSIZE, foodPos.y * CELLSIZE, CELLSIZE, CELLSIZE, darkGreen);        EndDrawing();    }    CloseWindow();}