feat: device on/off

1st.cpp

@@ -0,0 +1,16 @@
+class Device {
+public:
+    virtual void turnOn() = 0;
+    virtual void turnOff() = 0;
+    virtual ~Device() {}
+};
+
+class LED : public Device {
+public:
+    void turnOn() override {
+        // 點亮 LED
+    }
+    void turnOff() override {
+        // 熄滅 LED
+    }
+};