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` ````
<canvas id="canvas"></canvas>
```

` ````
body {
background: black;
margin: 0;
}
canvas {
background: white;
box-shadow: 1px 1px 1px rgba(0, 0, 0, .2);
}
```

` ````
var canvas = document.getElementById("canvas");
var context = canvas.getContext("2d");
var anim;
canvas.width = 600;
canvas.height = 400;
ships = [];
ships.push(new Ship(50, 100, 10, "blue")); // ships[0] is the MOVER
ships.push(new Ship(300, 200, 10, "red")); // ships[1] is static and shoots at [0]
function init(){
ships[0].setMoveTo(150, 250);
//ships[0].vx = ships[0].move.vx
if (ships[1].setTarget(ships[0])){
anim = setInterval(function(){
draw()
}, 30
);
} else console.log("no solution");
}
function Ship(x, y, s, color){
this.x = x;
this.y = y;
this.s = s;
this.color = color;
this.moveSpeed = 3 // my move speed
this.intercept; // placeholder for the intercept vector
this.interceptSpeed = 2// projectile speed
this.getTargetData = function(){
return {x: this.x, y: this.y};
}
this.setMoveTo = function(x, y){
this.move = new Vector({x: this.x, y: this.y}, {x: x, y: y}, this.moveSpeed);
}
this.setTarget = function(target){ // get the position of the intercept
//intercept(shooter, target, projSpeed){
var inter = getIntercept(this, target, target.move, this.interceptSpeed);
if (inter){
this.intercept = new Vector(this, inter, this.interceptSpeed);
return true;
} else this.intercept = false; return false;
}
this.draw = function(){ // draw myself (for the shooter)
context.beginPath();
context.arc(this.x, this.y, 10, 0, 2*Math.PI, false);
context.closePath();
context.fillStyle = this.color;
context.fill();
}
this.drawIntercept = function(){// draw a projectile, my this.intercept
if (!this.intercept.isDone()){
this.intercept.now++;
}
context.beginPath();
context.arc(
this.x + (this.intercept.vx * this.intercept.now),
this.y + (this.intercept.vy * this.intercept.now),
5, 0, 2*Math.PI, false
);
context.closePath();
context.fillStyle = "black";
context.fill();
}
this.drawMovement = function(){ // draw myself as the mover
if (!this.move.isDone()){
this.move.now++;
}
context.beginPath();
context.arc(
this.x + (this.move.vx * this.move.now),
this.y + (this.move.vy * this.move.now ),
10, 0, 2*Math.PI, false
);
context.closePath();
context.fillStyle = this.color;
context.fill();
}
}
function Vector(a, b, s){
this.a = a; // origin
this.b = b; // target
this.s = s;
this.x;
this.y;
this.now = 0; // current t
this.end; // max t aka magnitude
this.vx // velo x
this.vy // velo y
this.setup = function(){
this.x = b.x - a.x;
this.y = b.y - a.y;
var x = Math.pow(this.x, 2);
var y = Math.pow(this.y, 2);
var m = x + y;
this.m = Math.sqrt(m) / this.s
this.vx = this.x/this.m;
this.vy = this.y/this.m;
this.end = this.m;
};
this.isDone = function(){
if (this.now >= this.end){
return true;
}
}
this.setup();
}
function getDist(a, b){
return Math.sqrt((b.x-a.x)*(b.x-a.x) + (b.y-a.y)*(b.y-a.y));
}
function draw() {
context.clearRect(0, 0, canvas.width, canvas.height);
ships[0].drawMovement();
ships[1].draw();
ships[1].drawIntercept();
//console.log("ding")
if (ships[0].move.isDone() && ships[1].intercept.isDone()){
clearTimeout(anim)
}
}
function getIntercept(src, dst, dstV, v){
var tx = dst.x - src.x;
var ty = dst.y - src.y;
var tvx = dstV.vx;
var tvy = dstV.vy;
// Get quadratic equation components
var a = tvx*tvx + tvy*tvy - v*v;
var b = 2 * (tvx * tx + tvy * ty);
var c = tx*tx + ty*ty;
// Solve quadratic
var ts = quad(a, b, c); // See quad(), below
// Find smallest positive solution
var sol = null;
if (ts) {
var t0 = ts[0], t1 = ts[1];
var t = Math.min(t0, t1);
if (t < 0) t = Math.max(t0, t1);
if (t > 0) {
sol = {
x: dst.x + tvx * t,
y: dst.y + tvy * t
};
}
}
return sol;
}
function quad(a,b,c) {
var sol = null;
if (Math.abs(a) < 1e-6) {
if (Math.abs(b) < 1e-6) {
sol = Math.abs(c) < 1e-6 ? [0,0] : null;
} else {
sol = [-c/b, -c/b];
}
} else {
var disc = b*b - 4*a*c;
if (disc >= 0) {
disc = Math.sqrt(disc);
a = 2*a;
sol = [(-b-disc)/a, (-b+disc)/a];
}
}
return sol;
}
init();
// var dist = Math.sqrt(this.x * this.x + this.y * this.y);
```

999px

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