Solution to level 12 in Untrusted: http://alex.nisnevich.com/untrusted/

untrusted-lvl12-solution.js

/*
 * robotNav.js
 *
 * The green key is located in a slightly more
 * complicated room. You'll need to get the robot
 * past these obstacles.
 */

function startLevel(map) {
    // Hint: you can press R or 5 to "rest" and not move the
    // player, while the robot moves around.

    map.placePlayer(0, map.getHeight() - 1);
    var player = map.getPlayer();

    map.defineObject('robot', {
        'type': 'dynamic',
        'symbol': 'R',
        'color': 'gray',
        'onCollision': function (player, me) {
            me.giveItemTo(player, 'greenKey');
        },
        'behavior': function (me) {
            var relative = function(heading, direction) {
                var d = ['up', 'right', 'down', 'left'];
                var c = d.indexOf(heading) + direction;
                if (c > d.length - 1) c = c - d.length;
                if (c < 0) c = d.length + c;
                return d[c];
            }
            if (me.heading === undefined) me.heading = 'right';
            if (me.canMove(relative(me.heading, -1))) {
                me.heading = relative(me.heading, -1);
            } else {
                while (!me.canMove(me.heading)) {
                    me.heading = relative(me.heading, 1);
                }
            }
            me.move(me.heading);
            
            
        }
    });

    map.defineObject('barrier', {
        'symbol': '░',
        'color': 'purple',
        'impassable': true,
        'passableFor': ['robot']
    });

    map.placeObject(map.getWidth() - 1, map.getHeight() - 1, 'exit');
    map.placeObject(1, 1, 'robot');
    map.placeObject(map.getWidth() - 2, 8, 'greenKey');
    map.placeObject(map.getWidth() - 2, 9, 'barrier');

    for (var x = 0; x < map.getWidth(); x++) {
        map.placeObject(x, 0, 'block');
        if (x != map.getWidth() - 2) {
            map.placeObject(x, 9, 'block');
        }
    }

    for (var y = 1; y < 9; y++) {
        map.placeObject(0, y, 'block');
        map.placeObject(map.getWidth() - 1, y, 'block');
    }

    for (var i = 0; i < 4; i++) {
        map.placeObject(20 - i, i + 1, 'block');
        map.placeObject(35 - i, 8 - i, 'block');
    }
}

function validateLevel(map) {
    map.validateExactlyXManyObjects(1, 'exit');
    map.validateExactlyXManyObjects(1, 'robot');
    map.validateAtMostXObjects(1, 'greenKey');
}

function onExit(map) {
    if (!map.getPlayer().hasItem('greenKey')) {
        map.writeStatus("We need to get that key!");
        return false;
    } else {
        return true;
    }
}