Answers for "how to rotate a rectangle towards the mouse in html5 canvas"

how to rotate a rectangle towards the mouse in html5 canvas

var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');

var player = {
    x: 200,
    y: 200,
}

drawPlayer = function(something, angle) {
    context.clearRect(0, 0, 500, 500);
    context.beginPath();
    context.fillStyle = "blue";
    context.arc(something.x, something.y, 30, 0, 2 * Math.PI);
    context.fill();

    // save the untranslated context
    context.save();
    context.beginPath();
    // move the rotation point to the center of the player
    context.translate(something.x, something.y);
    context.rotate(angle);

    context.fillStyle = "red";
    // note that coordinates are translated, 
    // so 0 is player.x and -10 is player.y - 10
    context.fillRect(0, - 10, 50, 20);
    // restore the context to its untranslated state
    context.restore();
}

drawPlayer(player, 0);

document.onmousemove = function(e) { 
    var angle = Math.atan2(e.pageY - player.y, e.pageX - player.x)
    drawPlayer(player, angle);
}