```mermaid classDiagram class Vehicle { +int speed +String color +void startEngine() +void stopEngine() } class Car extends Vehicle { +int numberOfDoors +boolean sunroof +void openSunroof() +void closeSunroof() } class Truck extends Vehicle { +int loadCapacity +void loadCargo(Cargo cargo) +void unloadCargo() } class ElectricCar extends Car { +double batteryLevel +void chargeBattery() +void driveElectric() } class GasolineCar extends Car { +double fuelLevel +void refuel() +void driveGasoline() } class Cargo { +String type +double weight } class DeliveryTruck extends Truck { +String deliveryRoute +void deliverPackages() } class RefrigeratedTruck extends Truck { +boolean isRefrigerated +void coolCargo() } Vehicle <|-- Car Vehicle <|-- Truck Car <|-- ElectricCar Car <|-- GasolineCar Truck <|-- DeliveryTruck Truck <|-- RefrigeratedTruck ```