The loop() function causes draw() to execute continuously. If noLoop is called in setup() the draw() is only executed once. In this example click the mouse to execute loop(), which will cause the draw() the execute continuously.

float y = 100;
// The statements in the setup() function 
// run once when the program begins
void setup() {
  size(640, 360);  // Size should be the first statement
  stroke(255);     // Set stroke color to white
  y = height * 0.5;

// The statements in draw() are run until the 
// program is stopped. Each statement is run in 
// sequence and after the last line is read, the first 
// line is run again.
void draw() { 
  background(0);   // Set the background to black
  line(0, y, width, y);  
  y = y - 1; 
  if (y < 0) { 
    y = height; 

void mousePressed() {

Functions Used


Sets the color used to draw lines and borders around shapes

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Defines the dimension of the display window width and height in units of pixels

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The setup() function is run once, when the program starts

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Stops Processing from continuously executing the code within draw()

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Called directly after setup(), the draw() function continuously executes the lines of code contained inside its block until the program is stopped or noLoop() is called

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By default, Processing loops through draw() continuously, executing the code within it

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The mousePressed() function is called once after every time a mouse button is pressed

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Draws a line (a direct path between two points) to the screen

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The background() function sets the color used for the background of the Processing window

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