gistfile1.txt

'''mermaid
graph TD
    subgraph "Pen Housing"
        subgraph "Power Subsystem"
            A[Rechargeable Battery<br/>(e.g., Li-Po)] --> B[Power Management IC<br/>(Regulator & Charging Circuit)];
            B --> |VCC| C;
            B --> |VCC| G;
            B --> |VCC| H;
        end

        subgraph "Main Processing Unit"
            C[Microcontroller Unit (MCU)<br/>with Integrated Bluetooth Low Energy (BLE)];
            D[PCB Trace Antenna] <--> |RF Signal| C;
        end

        subgraph "Input Switches"
            E[Side Button Switch<br/>(Right Click)] --> |GPIO Signal| C;
            F[Pen Tip Pressure Switch<br/>(Left Click)] --> |GPIO Signal| C;
        end

        subgraph "Optical Navigation Subsystem (At Pen Tip)"
            G[Optical Mouse Sensor IC];
            H[Infrared (IR) LED];
            I[Lens Assembly<br/>(Prism & Focusing Lens)];

            G --> |Control| H;
            G --> |Motion Data (SPI/I2C)| C;

            H -.-> |IR Light Path| I;
            I -.-> |Reflected Light Path| G;
        end
        
        J[Writing Surface]
        I -.-> |Illumination| J
        J -.-> |Reflection| I
    end

    style C fill:#f9f,stroke:#333,stroke-width:2px
    style G fill:#ccf,stroke:#333,stroke-width:2px
    style E fill:#ff9,stroke:#333,stroke-width:1px
    style F fill:#ff9,stroke:#333,stroke-width:1px
    '''