function start_game() {
    let room = 'start';
    while (room != 'end') {
        if (room == 'start') {
            console.log('you are in a dark room. there is a door to the north.');
            let choice = prompt('> ');
            if (choice == 'north') {
                room = 'treasure';
            }
        } else if (room == 'treasure') {
            console.log('you found the treasure room. you win');
            room = 'end';
        }
    }
}

start_game();