* {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
    }

    body {
        background: #0f172a;
        color: #e5e7eb;
        font-family: Arial, sans-serif;
        display: flex;
        justify-content: center;
        padding: 20px;
    }

    .app {
        width: 100%;
        max-width: 600px;
        background: #020617;
        border-radius: 12px;
        padding: 16px;
        box-shadow: 0 0 20px rgba(0, 0, 0, 0.5);
        display: flex;
        flex-direction: column;
        gap: 10px;
    }

    .app-header {
        text-align: center;
        margin-bottom: 4px;
    }

    .app-header h1 {
        font-size: 22px;
        margin-bottom: 4px;
    }

    .app-header p {
        font-size: 12px;
        color: #9ca3af;
    }

    /* ---------- CHAT WINDOW ---------- */
    #chat-window {
        flex: 1;
        height: 60vh;
        border-radius: 8px;
        border: 1px solid #1f2937;
        padding: 10px;
        overflow-y: auto;
        background: #020617;
    }

    .message {
        margin: 8px 0;
        max-width: 80%;
        padding: 8px 12px;
        border-radius: 12px;
        line-height: 1.4;
        font-size: 14px;
        white-space: pre-wrap;
    }

    .message.user {
        background: #1d4ed8;
        margin-left: auto;
        text-align: right;
    }

    .message.bot {
        background: #111827;
        border: 1px solid #1f2937;
        margin-right: auto;
    }

    .message.system {
        background: #0f172a;
        border: 1px dashed #374151;
        margin: 4px auto;
        font-size: 12px;
        color: #9ca3af;
        text-align: center;
    }

    /* ---------- FORM ---------- */
    #chat-form {
        display: flex;
        gap: 8px;
        margin-top: 4px;
    }

    #user-input {
        flex: 1;
        padding: 8px 10px;
        border-radius: 8px;
        border: 1px solid #374151;
        outline: none;
        background: #020617;
        color: #e5e7eb;
        font-size: 14px;
    }

    #user-input::placeholder {
        color: #6b7280;
    }

    button {
        padding: 8px 14px;
        border-radius: 8px;
        border: none;
        cursor: pointer;
        background: #22c55e;
        color: #020617;
        font-weight: bold;
        font-size: 14px;
        transition: transform 0.1s ease, opacity 0.1s ease;
        white-space: nowrap;
    }

    button:hover {
        opacity: 0.9;
        transform: translateY(-1px);
    }

    button:active {
        transform: translateY(0);
    }