Solution to level 7 in Untrusted: http://alex.nisnevich.com/untrusted/

untrusted-lvl7-solution.js

/*************
* colors.js *
 *************
 *
 * You're almost at the exit. You just need to get past this
 * color lock.
 *
 * Changing your environment is no longer enough. You must
 * learn to change yourself. I've sent you a little something
 * that should help with that.
 */

function startLevel(map) {
    map.placePlayer(0, 12);

    map.placeObject(5, 12, 'phone');

    // The function phone lets you call arbitrary functions,
    // as defined by player.setPhoneCallback() below.
    // The function phone callback is bound to Q or Ctrl-6.
    map.getPlayer().setPhoneCallback(function () {
        var player = map.getPlayer();
        
        player.step = player.step || 0;
        
        switch (player.step) {
        case 0:
        case 3:
            player.setColor('#f00');
            break;
        case 1:
        case 4:
            player.setColor('#ff0');
            break;
        case 2:
            player.setColor('#0f0');
            break;
        }
        
        player.step ++;

    });


    map.defineObject('redLock', {
        symbol: '☒',
        color: "#f00", // red
        impassable: function(player, object) {
            return player.getColor() != object.color;
        }
    });

    map.defineObject('greenLock', {
        symbol: '☒',
        color: "#0f0", // green
        impassable: function(player, object) {
            return player.getColor() != object.color;
        }
    });

    map.defineObject('yellowLock', {
        symbol: '☒',
        color: "#ff0", // yellow
        impassable: function(player, object) {
            return player.getColor() != object.color;
        }
    });

    for (var x = 20; x <= 40; x++) {
        map.placeObject(x, 11, 'block');
        map.placeObject(x, 13, 'block');
    }
    map.placeObject(22, 12, 'greenLock');
    map.placeObject(25, 12, 'redLock');
    map.placeObject(28, 12, 'yellowLock');
    map.placeObject(31, 12, 'greenLock');
    map.placeObject(34, 12, 'redLock');
    map.placeObject(37, 12, 'yellowLock');
    map.placeObject(40, 12, 'exit');
    for (var y = 0; y < map.getHeight(); y++) {
        if (y != 12) {
            map.placeObject(40, y, 'block');
        }
        for (var x = 41; x < map.getWidth(); x++) {
            map.setSquareColor(x, y, '#080');
        }
    }
}

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

function onExit(map) {
    if (!map.getPlayer().hasItem('phone')) {
        map.writeStatus("We need the phone!");
        return false;
    } else {
        return true;
    }
}