var speed = 0.05;

var span = 10;

​

function setup() {

  createCanvas(800, 800);

}

​

function draw() {

  background(0,156,209);

  fill(255);

  noStroke();

  speed = map(mouseX,0,width,0,0.25);

  span = map(mouseY,0,height,0.1,50);

  text("speed:" + speed,width-120,30);

  text("span:" + span,width-120,50);

  noFill();

  stroke(255);

  drawCrv();

}

​

function drawCrv(){

  beginShape();

  curveVertex(-5,height/2);

  for(var i=0;i<width+span;i+=span){

    curveVertex(i,height/2+sin(i-frameCount*speed)*amp);

  }

  curveVertex(width+5,height/2);

  endShape();

}