// Set the window size to 200 wide and 200 tall
size(200,200);

// Make the background red.  Red is the first argument and is set to the maximum value.
// Blue is the second argument and set to nothing
// Same Green.  
background(255,0,0);

// Make what we draw filled with yellow from this point forward
// Yellow = Red and Green
fill(200,200,0);

// Color any points or lines black from this point forward
stroke(0,0,0);

/* 
  Draw a line from 5 on the x axis and 10 on the y axis to 
  15 on the x axis and 10 on the y axis.
  This uses the stroke color
*/
line(5,10,15,10);

/*
  Draw an rectangle.  Start at 22,15 end at 50,100.
  Filled with our fill color (yellow), set above
*/
rect(22,15,50,100);