Arduino program to render a basic Snake effect on an Adafruit Matrix Portal attached to a 32x64 LED matrix

snake.ino

#include <Adafruit_SleepyDog.h>
#include <Adafruit_Protomatter.h>

#define HEIGHT 32
#define WIDTH 64
#define LED_COUNT (HEIGHT*WIDTH)

uint8_t rgbPins[]  = {7, 8, 9, 10, 11, 12};
uint8_t addrPins[] = {17, 18, 19, 20};
uint8_t clockPin   = 14;
uint8_t latchPin   = 15;
uint8_t oePin      = 16;

Adafruit_Protomatter matrix(64, 4, 1, rgbPins, 4, addrPins, clockPin, latchPin, oePin, true);

struct segment_t {
  uint8_t x;
  uint8_t y;
};

segment_t init_segments[LED_COUNT] = {
  segment_t { 9, 0 },
  segment_t { 8, 0 },
  segment_t { 7, 0 },
  segment_t { 6, 0 },
  segment_t { 5, 0 },
  segment_t { 4, 0 },
  segment_t { 3, 0 },
  segment_t { 2, 0 },
  segment_t { 1, 0 },
  segment_t { 0, 0 },
};

struct snake_t {
  uint16_t segment_count;
  segment_t *segments;
};

segment_t food = {23, 15};

snake_t snake = {
  10,
  init_segments
};

void snake_move(snake_t *snake, int16_t dx, int16_t dy) {
  uint8_t new_head_x = snake->segments[0].x + dx;
  uint8_t new_head_y = snake->segments[0].y + dy;
  if (food.x == new_head_x && food.y == new_head_y) {
    snake->segment_count++;
    /*snake->segments = realloc(snake->segments, snake->segment_count);*/
  }
  for (int i = snake->segment_count-1; i > 0; i--) {
    snake->segments[i] = snake->segments[i-1];
  }
  snake->segments[0].x += dx;
  snake->segments[0].y += dy;
}

void setup(void) {
  Serial.begin(115200);

  ProtomatterStatus status = matrix.begin();
  Serial.print("Protomatter begin() status: ");
  Serial.println((int)status);
  if(status != PROTOMATTER_OK) {
    for(;;);
  }
  matrix.show();
}

void loop(void) {
  if (food.x == snake.segments[0].x && food.y == snake.segments[0].y) {
    food.x = (food.x * 9 + snake.segment_count) % WIDTH;
    food.y = (food.y * 7 + snake.segment_count) % HEIGHT;
  }

  matrix.fillScreen(0x0);

  matrix.drawPixel(
    snake.segments[snake.segment_count-1].x, 
    snake.segments[snake.segment_count-1].y, 
    matrix.color565(0, 0, 0)
  );
  int16_t dx = 0;
  int16_t dy = 0;
  dx = food.x - snake.segments[0].x;
  dx /= abs(dx);
  dy = food.y - snake.segments[0].y;
  dy /= abs(dy);
  if (dx != 0 && dx != 0) {
    if (abs(dy) > abs(dx)) {
      dx = 0;
    } else {
      dy = 0;
    }
  }
  
  snake_move(&snake, dx, dy);
  if (snake.segment_count > LED_COUNT) {
    reset();
  }
  uint16_t intensity_loss_per_segment = 24500 / (uint16_t) snake.segment_count;
  for (int16_t i = snake.segment_count-1; i >= 0; i--) {
    uint8_t intensity = 255 - (uint8_t) ((intensity_loss_per_segment * i) / 100);
    matrix.drawPixel(snake.segments[i].x, snake.segments[i].y, matrix.color565(0, intensity, 0));
  }
  
  matrix.drawPixel(food.x, food.y, matrix.color565(255, 255, 255));
  //noInterrupts();
  matrix.show();
  //interrupts();
  
  delay(2); //50); //10); //2); //100);
}

void reset() {
  // Make a watchdog timer expire, to trigger a board reset
  Watchdog.enable(1);
  while (true) {}
}