Conway's game of life for the Meggy Jr

MeggyJrGameOfLife.c

#include <stdlib.h>
#include <MeggyJrSimple.h>

byte screen[8][8] = {{0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0}};

const byte LIVE = 4;
const byte DEAD = 0;
const byte CURSOR = 1;
byte current = 0;
char cursorx, cursory, iteration = 0;
boolean paused = true;

void setup() {
  MeggyJrSimpleSetup();
  display();
}

void loop() {
  CheckButtonsPress();
  
  if (Button_A)
    paused = !paused;
  
  if (!paused)
    game_loop();
  else
    iterate_pause();
  
  display();
}

void game_loop() {
  delay(500);
  copy_display(screen);
  ClearSlate();
  byte board[8][8] = {{0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0},
                     {0,0,0,0,0,0,0,0}};
  iterate(board);
  iteration++;
  
  int i;
  for (i=0; i<8; i++) {
    int j;
    for (j=0; j<8; j++) {
      screen[i][j] = board[i][j];
    }
  }
}

// Display screen buffer
void display() {
  SetAuxLEDs(iteration);
  int i;  
  for (i=0; i<8; i++) {
    int j;
    for (j=0; j<8; j++) {
      DrawPx(j, 7-i, screen[i][j]);
    }
  }
  
  if (paused)
    DrawPx(cursory, 7-cursorx, CURSOR);
  
  DisplaySlate();
}

// Copy the screen buffer to board
void copy_display(byte board[][8]) {
  int i;
  for (i=0; i<8; i++) {
    int j;
    for (j=0; j<8; j++) {
     board[i][j] = ReadPx(j, 7-i);
    }
  }
}

// A single iteration of gameoflife
void iterate(byte board[][8]) {
  int i;
  for (i=0; i<8; i++) {
    int j;
    for (j=0; j<8; j++) {
      int neighbours = live_neighbours(screen, i, j);
      switch (neighbours) {
        case 0:
        case 1:
          board[i][j] = DEAD;
          break;
        case 2:
          if (screen[i][j] == LIVE)
            board[i][j] = LIVE;
          break;
        case 3:
          if (screen[i][j] == LIVE)
            board[i][j] = LIVE;
          if (screen[i][j] == DEAD)
            board[i][j] = LIVE;
          break;
        case 4:
        case 5:
        case 6:
        case 7:
        case 8:
          if (screen[i][j] == LIVE)
            board[i][j] = DEAD;
          break;
      }
    }
  }
}

// Returns the number of live neighbours for a given position and board
char live_neighbours(byte board[8][8], char i, char j) {
  char neighbours = 0;
  
  char above = i-1;
  char below = i+1;
  char left = j-1;
  char right = j+1;
  
  // wrap everything around
  if (above == -1)
    above = 7;
  if (below == 8)
    below = 0;
  if (left == -1)
    left = 7;
  if (right == 8)
    right = 0;
  
  // check neighbours
  if (board[above][left] == LIVE)
    neighbours++;
  if (board[above][j] == LIVE)
    neighbours++;
  if (board[above][right] == LIVE)
    neighbours++;
  if (board[i][left] == LIVE)
    neighbours++;
  if (board[i][right] == LIVE)
    neighbours++;
  if (board[below][left] == LIVE)
    neighbours++;
  if (board[below][j] == LIVE) 
    neighbours++;
  if (board[below][right] == LIVE)
    neighbours++;
 
  return neighbours;  
}

void iterate_pause() {
  if (Button_B) {
    screen[cursorx][cursory] = LIVE;
  }
  else if(Button_Right) {
    cursory++;
    if (cursory == 8)
      cursory = 0;
  }
  else if(Button_Left) {
    cursory--;
    if (cursory == -1)
      cursory = 7;
  }
  else if(Button_Up) {
    cursorx--;
    if (cursorx == -1)
      cursorx = 7;
  }
  else if(Button_Down) {
    cursorx++;
    if (cursorx == 8)
      cursorx = 0;
  }
}