map.defineObject('selfDefenceDrone', {
'type': 'dynamic',
'symbol': 'X',
'color': 'green',
'onCollision': function (player) {
player.killedBy('an attack drone');
console.log('killled!');
},
'behavior': function (me) {
moveToward(me, 'attackDrone');
console.log(me.findNearest('attackDrone'));
console.log('-------------');
}
});

map.placeObject(map.getWidth()-9, 12, 'selfDefenceDrone');
map.placeObject(map.getWidth()-5, 16, 'selfDefenceDrone');
map.placeObject(map.getWidth()-5, 8, 'selfDefenceDrone');
map.placeObject(map.getWidth()-1, 14, 'selfDefenceDrone');