flowchart TD
    %% Define Styles
    classDef client fill:#e1f5fe,stroke:#01579b,stroke-width:2px;
    classDef sensor fill:#fff9c4,stroke:#fbc02d,stroke-width:2px;
    classDef action fill:#e8f5e9,stroke:#2e7d32,stroke-width:2px;
    classDef captive fill:#ffe0b2,stroke:#ef6c00,stroke-width:2px,stroke-dasharray: 5 5;

    subgraph User_Action [User Action]
        Start((User Opens Browser
Enters URL)) --> GenDNS["Client Sends DNS Query
e.g. query www.google.com"]
    end

    subgraph Sensor_Interception [Sensor Interception & Response]
        GenDNS -- Packet passes through Sensor --> DetectDNS["Sensor Intercepts DNS Packet"]
        DetectDNS --> DNSHijack["Sensor Performs DNS Hijacking
Replies A Record = Sensor IP"]
        DNSHijack -- DNS Response --> ClientRecv["Client Receives Sensor IP"]
    end

    subgraph Connection_Handling [Connection Setup & Redirection]
        ClientRecv --> EstConn["Client Connects to Sensor IP
Initiates TCP Connection"]
        EstConn --> CheckPort{"Check Port Type"}
        
        CheckPort -- Port 80 HTTP --> Redir80["Sensor Web Server
Replies HTTP 302 Redirect"]
        CheckPort -- Port 443 HTTPS --> Handshake443["Poseidon Takes Over Port 443
SSL Handshake (Self-signed Cert)"]
    end

    subgraph Browser_Reaction [Browser Reaction & Captive Portal]
        Handshake443 -- "Certificate Error (HSTS or HTTPS)" --> TriggerCP["Trigger Captive Portal Detection
(Connects to connectivitycheck...)"]
        TriggerCP -- "Send HTTP Probe Packet" --> RedirCP["Sensor Intercepts HTTP
Replies 302 Redirect"]
    end

    subgraph Result [Final Result]
        Redir80 --> ShowBlock["Display Block Page"]
        RedirCP --> ShowBlock
    end

    class Start,GenDNS,ClientRecv,EstConn client
    class DetectDNS,DNSHijack,Redir80,Handshake443,RedirCP sensor
    class ShowBlock action
    class TriggerCP captive