Solution to level 16 in Untrusted: http://alex.nisnevich.com/untrusted/

untrusted-lvl16-solution.js

/*************
 * lasers.js *
 *************
 *
 * Time to unleash the killer lasers! Each laser will kill you
 * unless you have the appropriate color. Too bad you can't
 * see which color corresponds to which laser!
 */

function getRandomInt(min, max) {
    return Math.floor(Math.random() * (max - min + 1)) + min;
}

function startLevel(map) {
    map.placePlayer(0, 0);
    map.placeObject(map.getWidth()-1, map.getHeight()-1, 'exit');
    var player = map.getPlayer();

    for (var i = 0; i < 25; i++) {
        var colors = ['red', 'yellow', 'teal'];

        var startX = getRandomInt(0, 600);
        var startY = getRandomInt(0, 500);
        var angle = getRandomInt(0, 360);
        var length = getRandomInt(200, 300);
        var color = colors[i % 3];
        createLaser(startX, startY, angle, length, color);
    }

    function createLaser(centerX, centerY, angleInDegrees, length, color) {
        var angleInRadians = angleInDegrees * Math.PI / 180;

        var x1 = centerX - Math.cos(angleInRadians) * length / 2;
        var y1 = centerY + Math.sin(angleInRadians) * length / 2;
        var x2 = centerX + Math.cos(angleInRadians) * length / 2;
        var y2 = centerY - Math.sin(angleInRadians) * length / 2;

        // map.createLine() creates a line with an effect when
        // the player moves over it, but doesn't display it
        map.createLine([x1, y1], [x2, y2], function (player) {
            if (player.getColor() != color) {
                player.killedBy('a ' + color + ' laser');
            }
        });

        // using canvas to draw the line
        var ctx = map.getCanvasContext();
        ctx.beginPath();
        ctx.strokeStyle = color;//'white';
        ctx.lineWidth = 5;
        ctx.moveTo(x1, y1);
        ctx.lineTo(x2, y2);
        ctx.stroke();

    }


    

    player.setPhoneCallback(function(){
        if (player.getColor() == 'red'){
            player.setColor('yellow');
        } else if (player.getColor() == 'yellow') {
            player.setColor('teal');
        } else {
            player.setColor('red');
        }
    
    });





}

function validateLevel(map) {
    map.validateExactlyXManyObjects(1, 'exit');
    map.validateAtLeastXLines(25);
}