Editing Aiming

<edcode>

var t=0.0;
var speed=0.02;
var ax=100;
var ay=320;

var bx=400;
var by=200;

var annotation = "";
var dataNote = "";
var dataNote2 = "";

function loop() {
  if (t>=1) t=0;
}

function setDefaults() {
  ax=100;
  ay=320;
  bx=400;
  by=200;
  speed=0.02;
  annotation = "";
  dataNote = "";
  dataNote2 = "";
}

function ss(v,a,b) {
  var w=v*v*v*(v*(v*6-15)+10);
  return(1.0-w)*a+(w*b); 
}

function transition(a,b) {
  return ss(t,a,b);
}

function wiggle(a,b) {
  
  var w=t*2;
  if (w>1) w=2-w;
  return ss(w,a,b);
}

function spots() {
  setColour("red");
  fillCircle(ax,ay,7);
  setColour("purple");
  fillCircle(bx,by,7);
  
  annotation="We want to move the red point towards the purple point";
}

function hvLines() {
  spots();
  setColour("blue");
  drawLine(ax,ay,bx,ay);
  setColour("green");
  drawLine(ax,ay,ax,by);
  
  annotation="We know the difference in x and y values for the two points";
  
}

function hvLines_transition() {
  spots();
  setColour("blue");
  drawLine(ax,ay,bx,ay);
  setColour("green");

  annotation="Combining the lines makes a path from one to the other";

  drawLine(transition(ax,bx),ay,transition(ax,bx),by);
}

function pale_hvLines() {
  spots();
  setColour("lightblue");
  drawLine(ax,ay,bx,ay);
  setColour("lightgreen");
  drawLine(bx,ay,bx,by);  
  setColour("magenta");
  drawLine(ax,ay,bx,by);  
}

function triangleNote() {
  var dx= bx-ax;
  var dy= by-ay;
  var d = Math.sqrt(dx*dx+dy*dy);
  
  dataNote = "Distance from ax,ay to bx,by is " +d.toFixed(1);
}

function triangle() {
  spots();
  setColour("blue");
  drawLine(ax,ay,bx,ay);
  setColour("green");
  drawLine(bx,ay,bx,by);  
  setColour("magenta");
  drawLine(ax,ay,bx,by);  
  
  annotation="Adding the straight line to the target makes a right angled triangle";

  triangleNote();  
}             


function vector(newLength) {
  var dx= bx-ax;
  var dy= by-ay;
  var d = Math.sqrt(dx*dx+dy*dy);
      
  
  dx/=d;
  dy/=d;
  setColour("black");
  drawLine(ax,ay-1,ax+dx*newLength,ay-1+dy*newLength);
  drawLine(ax,ay+1,ax+dx*newLength,ay+1+dy*newLength);
  
}

function vector_transition() {
  triangle();
  vector(transition(0,30));
  annotation="We want to move a fixed distance along this line";
  dataNote+=", we want to move a distance of 30";
}

function move_around() {
  bx=wiggle(bx,40);
  by=wiggle(by,300);
  ax=wiggle(ax,ax+30);
  ay=wiggle(ay,ay+30);
  triangle();
  vector(30);
  speed=0.003;
  loop();
  annotation="When the points are different the distance should stay the same";
  dataNote+=", we want to move a distance of 30";
}

function stopped() {
  triangle();
  vector(30);
  annotation="To find x and y movement we reduce both values by the same amount";
  dataNote+=", we want to move a distance of 30";
}

function show_parts() {
  pale_hvLines();
  
  vector(30);
  
  setColour("blue");
  
  var dx= bx-ax;
  var dy= by-ay;
  var d = Math.sqrt(dx*dx+dy*dy);
  dx/=d;
  dy/=d;
  var scale = transition(d,30);
  
  drawLine(ax,ay,ax+dx*scale,ay);
  setColour("green");
  drawLine(ax+dx*scale,ay,ax+dx*scale,ay+dy*scale);  
  
  speed=0.001;

  annotation="The angles stay the same if the sides are divided by the same amount";
  triangleNote();  
  dataNote+=", we want to move a distance of 30";

  var newdx=dx*scale;
  var newdy=dy*scale;
  var newd = Math.sqrt(newdx*newdx+newdy*newdy);
  var div = d/newd*30; 
  dataNote2=" "+d.toFixed(1)+ " / " +div.toFixed(1) +" * 30 = "  +(newd).toFixed(1);
}


var parts=[spots, hvLines, hvLines_transition,triangle,vector_transition,move_around,stopped,show_parts];
var part=0;

function update() {
  setDefaults();  
  clear();
  parts[part]();

  setColour("black");
  print(annotation);

  setColour("grey");
  print("ax = "+ax.toFixed(0)+"     bx = "+bx.toFixed(0)+"            dx = bx-ax = " + (bx-ax).toFixed(0) ,100,370);
  print("ay = "+ay.toFixed(0)+"     by = "+by.toFixed(0)+"            dy = by-ay = " + (bx-ax).toFixed(0) ,100,400);
  print(dataNote,4,430);
  print(dataNote2,4,460);
  
  t+=speed;
  if (t>1) {
    t=1;
  }

  
  if (keyWentDown(32)) {
    t=0;
    part+=1;
    if (part>=parts.length) {
      part =0;
    }
  }
  
  
}

run(update);
</edcode>