/// fishtank
float left=50,top=50,right=550,bottom=350;
float fishX=left, fishY=top+10; 
float fishDX=3, fishDY=2;

Pisces moe, curly, larry; 

void setup() {
  size(600,500);
  moe=  new Pisces();  moe.r=255;
  moe.x=100;  moe.y=100;
  curly=  new Pisces();  curly.g=255;
  curly.x=200;  curly.y=200;
  larry= new Pisces();  larry.b=255;
  larry.x=300;  larry.y=300;
}

void draw() {
  scene();
  fish(); 
  movefish();
  showfish();
}
void movefish() {
  //
  moe.move();
  curly.move();
  larry.move();
  //
}
void showfish() {
  //
  moe.show();
  curly.show();
  larry.show();
  //
}

void scene() {
  background(27, 247, 87); 
  fishtank ();
}


void fishtank() { 
  fill(77, 112, 247);
  stroke(1);
  strokeWeight(5);
  rectMode(CORNERS);
  rect(left,top,right,bottom);
}

void fish() {
  if (fishX<left || fishX>right) fishDX= -fishDX;
  if (fishY<top || fishY>bottom) fishDY= -fishDY;
  fishDY=  fishDY + random( -0.05, +0.075 );
  if (abs(fishDY) > 10) fishDY /= 10;
  fishX += fishDX;
  fishY += fishDY;
  // show
  strokeWeight (1);
  fill(255,255,0);
  ellipse(fishX,fishY,45,20 );
}

class Pisces {
  //// Fish moves, draws, etc.
  float x=50, y=50;
  float dx=3, dy=2;
  int r, g, b;
  // METHODS //
  void move() {
    if (x<left || x>right) dx= -dx;
    if (y<top || y>bottom) dy= -dy;
    dy=  dy + random( -0.05, +0.075 );
    if (abs(dy) > 10) dy /= 10;
    x += dx;
    y += dy;
  }
  // show
  void show() {
    strokeWeight (1);
    fill(r,g,b);
    ellipse(x,y,45,20 );
  }
}