'Rotate' gradient background

[glv]

Hello @Erif ,

You can also fill() a vertex in a shape.

There is a cool example that comes with Processing in:
File > Examples … > Topics> Geometry > RGBCube

An example I cooked up:

// Gradient Shape
// v1.0.0
// GLV 2022-12-03

void setup()  
  { 
  size(800, 400, P2D); 
  noStroke(); 
  }   
 
void draw()  
  { 
  background(0);
  
  colorMode(RGB);
  
  translate(width/4, height/2); 
  beginShape(QUADS);
  fill(0, 255, 255); vertex(-150,  150);
  fill(255, 255, 255); vertex( 150,  150);
  fill(255, 0, 255); vertex( 150, -150);
  fill(0, 0, 255); vertex(-150, -150);
  endShape();
  
  translate(width/2, 0); 
  
  colorMode(HSB, 360, 100, 100);
  
  beginShape(QUADS);
  fill((frameCount+0)%360, 100, 100); vertex(-150,  150);
  fill((frameCount+90)%360, 100, 100); vertex( 150,  150);
  fill((frameCount+180)%360, 100, 100); vertex( 150, -150);
  fill((frameCount+270)%360, 100, 100); vertex(-150, -150);
  endShape();
  } 

:)