size(600,400);
float brickHeight = 15;

fill(178,34,34);       // brick red
stroke(205,205,193);   // mortar color
strokeWeight(3);

int row = 0;
while (row*brickHeight < height) {
  // draw one more row
  float offset = -1.5 * brickHeight * (row % 2);
  int count = 0;
  while (3*brickHeight*count + offset < width) {
      // draw one more brick in current row
      rect(offset+3*brickHeight*count, row*brickHeight,
           3*brickHeight, brickHeight);
      count++;
  }
  row++;
}