Problem with Game of Life

Processing Coding Questions
6

Setting dimensions to rectangle gave hint where the problem is. You had mixed rows and columns (x goes along horizontal axis so it matches columns). Once I replaced columns and rows things seem to work fine.

int spacer = 5;
int cols;
int rows;
int covid;
int initialCarrier = 100;
int chanceCured = 8;
int chanceSick = 4;
color fillCol = color(255, 255, 255);
boolean[][][] grid;

void setup() {
  size(1200, 800);
  rows = height/spacer;
  cols = width/spacer;
  covid = 2;
  grid = new boolean[cols][rows][covid];
  for (int y = 0; y < rows; y++) {
    for (int x = 0; x < cols; x++) {
      grid[x][y][1] = false;

      int rnd = floor(random(2));
      if (rnd == 1) {
        grid[x][y][0] = true;
      }

      if (grid[x][y][0] ) {
        int infect = floor(random(initialCarrier));
        if (infect == 1) {
          grid[x][y][1] = true;
        };
      }
    }
  }
}

void draw() {
  background(0);
  frameRate(5);
  noStroke();
  for (int y = 0; y < rows; y ++) {
    for (int x = 0; x < cols; x ++) {

      // cured
      if (grid[x][y][1]) {
        int cured = floor(random(chanceCured));
        if (cured == 1) {
          grid[x][y][1] = false;
        };
        if (cured == 2) {
          grid[x][y][1] = false;
          grid[x][y][0] = false;
        };
      }

      /// if contaminated
      if (grid[x][y][1] && grid[x][y][0]) {
        fillCol = color(0, 255, 0);
        fill(fillCol);
      }


      // not contaminated
      else if (grid[x][y][0] && !grid[x][y][1]) {

        int species = 0;
        // previous
        //for ( int i= -1; i<2; i++) {
        //  for ( int j= -1; j<2; j++) {
        //    int mody = (y + j + cols) % cols;
        //    int modx = (x + i + rows) % rows;
        //    if (grid[modx][mody][0]) {
        //      species +=1;
        //    }
        //  }
        //}


        // new basic calc
        for (int i = -1; i < 2; i++) {
          for (int j = -1; j < 2; j++) {
            int nX = x+j;
            int nY = y+i;

            if (nX <= 0) {
              nX = 0;
            }
            if (nY <= 0) {
              nY = 0;
            }
            if (nX >= cols-1) {
              nX = cols-1;
            }
            if (nY >= rows-1) {
              nY = rows-1;
            }
            if (grid[nX][nY][0]) {
              species += 1;
            }
          }
        }
        species -= 1;
        if (species > 6) {
          fillCol = color(255, 255, 255);
        } else if (species > 4) {
          fillCol = color(255, 0, 0);
        } else if (species > 2) {
          fillCol = color(0, 0, 255);
        } else {
          fillCol = color(0, 0, 100);
        }

        fill(fillCol);
      } else {
        fill(0, 0, 0);
      };

      rect(x*spacer, y*spacer, spacer, spacer);
    }
  }
  updateGrid();
}

void updateGrid() {
  boolean[][][] child = grid;

  for (int y = 0; y < rows; y++) {
    for (int x = 0; x < cols; x++) {
      if (!grid[x][y][1]) {
        boolean alive = grid[x][y][0];

        int species = 0;

        // check neighbour v2
        for (int i = -1; i < 2; i++) {
          for (int j = -1; j < 2; j++) {
            int nX = x+i;
            int nY = y+j;

            if (nX <= 0) {
              nX = 0;
            }
            if (nY <= 0) {
              nY = 0;
            }
            if (nX >= cols-1) {
              nX = cols-1;
            }
            if (nY >= rows-1) {
              nY = rows-1;
            }
            if (grid[nX][nY][0]) {
              species += 1;
            }

            //if neighbour contagious
            if (grid[nX][nY][1]) {
              int contagious = floor(random(chanceSick));
              if (contagious < 2 && alive) {
                child[x][y][1] = true;
              }
            }
          }
        }

        // check neighbour
        //for ( int i= -1; i<2; i++) {
        //  for ( int j= -1; j<2; j++) {
        //    int modi = (x + i + cols) % cols;
        //    int modj = (y + j + rows) % rows;

        //    // if neighbour contagious
        //    if (grid[modj][modi][1]) {
        //        int contagious = floor(random(chanceSick));
        //        if (contagious < 2 && alive) {
        //          child[x][y][1] = true;
        //        }
        //      }

        //      // add neighbour
        //      if (grid[modj][modi][0]) {
        //        species +=1;
        //      }
        //    }
        //  }

        if (alive) {
          species -= 1;
        }

        if (!alive && species == 3) {
          child[x][y][0] = true;
        } else if (alive && (species < 2 || species > 3)) {
          child[x][y][0] = false;
          child[x][y][1] = false;
        }
      }
    }
  }
  grid = child;
}