/**
 * Three-color checkerboard.
 *
 * <p>Elie Zananiri<br>
 * CART 253, Winter 2008</p>
 */

/*------- global variables ----------*/
int cellSize = 20;  // size of our rectangles

// counter to tracks which color to use as fill
// can have three possible states: 0, 1, 2
int currColor = 0;

// counter to tracks the first color of the current column
// ensures that we end up with a checkerboard instead of solid columns
int initialColor = 0;

/*------- initialization ------------*/
void setup() {
  size(300, 300);
  background(255);
  noStroke();
}

/*------ function definitions -------*/
// draws a checkerboard pattern 
void drawPattern() {
  // walk across the x-axis
  for (int x=0; x < width; x = x+cellSize) {
    // walk down the y-axis
    for (int y=0; y < height; y = y+cellSize) {
      if (currColor%3 == 0) {
        fill(255, 212, 0);
      } else if (currColor%3 == 1) {
        fill(255, 254, 96);
      } else {
        fill(247, 147, 30);
      }
      
      rect(x, y, cellSize, cellSize);
      currColor++;
    }

    // column is finished, advance the counter for initialColor
    setInitialFill();
  }
}

// advances the counter that determines the color of the first cell of a column
void setInitialFill() {
  if (initialColor == 0) {
    currColor = initialColor = 1;
  } else if (initialColor == 1) {
    currColor = initialColor = 2;
  } else {
    currColor = initialColor = 0;
  }
}

/*------ main loop ------------------*/
void draw() {
  drawPattern();
}