Polytopia unit battle

public function getBattleResult(attacker:WorldObject, defender:WorldObject) : Object
      {
         var _magic_:* = 4.5;
         var _attk_:Number = attacker.attack * (attacker.health / attacker.maxHealth);
         var _deff_:Number = defender.defence * (defender.health / defender.maxHealth);
         var _sum_:Number = _attk_ + _deff_;
         var _attack_:Number = Math.round(_attk_ / _sum_ * attacker.attack * _magic_);
         var _defence_:* = -1;
         if(defender.tile.getAttackRange(defender.owner).indexOf(attacker.tile) > -1)
         {
            _defence_ = Number(Math.round(_deff_ / defender.defenceBonus / _sum_ * defender.defence * _magic_));
         }
         var _proceed_:Boolean = false;
         if(attacker is Unit && defender.health <= _attack_ && attacker.range == 1 && Boolean(defender.tile.moveOk(attacker as Unit)))
         {
            _proceed_ = true;
         }
         return {
            "attack":_attack_,
            "defence":_defence_,
            "proceed":_proceed_
         };
      }