This example is for Processing 3+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.
Linear Motion.
Changing a variable to create a moving line. When the line moves off the edge of the window, the variable is set to 0, which places the line back at the bottom of the screen.
float a; void setup() { size(640, 360); stroke(255); a = height/2; } void draw() { background(51); line(0, a, width, a); a = a - 0.5; if (a < 0) { a = height; } }