/* WhatsApp-like Styles */
    .chat-layout { display: flex; height: calc(100vh - 80px); background: #fff; border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow-sm); border: 1px solid var(--border-color); }
    .chat-sidebar { width: 350px; border-right: 1px solid var(--border-color); display: flex; flex-direction: column; background: #fff; }
    .chat-main { flex: 1; display: flex; flex-direction: column; background: #efeae2; /* WhatsApp-ish bg */ position: relative; }

    .chat-search { padding: 10px; background: #f0f2f5; border-bottom: 1px solid var(--border-color); }
    .user-list { flex: 1; overflow-y: auto; }

    .user-item {
        display: flex; align-items: center; gap: 15px; padding: 12px 15px; cursor: pointer; border-bottom: 1px solid #f0f2f5; transition: 0.2s;
    }
    .user-item:hover { background: #f5f6f6; }
    .user-item.active { background: #f0f2f5; }

    .avatar { width: 45px; height: 45px; border-radius: 50%; background: #dfe3e5; display: flex; justify-content: center; align-items: center; font-size: 1.2rem; color: #fff; flex-shrink: 0; }

    .chat-header { padding: 10px 15px; background: #f0f2f5; border-bottom: 1px solid var(--border-color); display: flex; align-items: center; gap: 15px; height: 60px; }
    .chat-messages { flex: 1; overflow-y: auto; padding: 20px; display: flex; flex-direction: column; gap: 8px; }

    .message { max-width: 65%; padding: 8px 12px; border-radius: 7.5px; position: relative; font-size: 0.95rem; line-height: 1.4; box-shadow: 0 1px 0.5px rgba(0,0,0,0.13); }
    .msg-sent { align-self: flex-end; background: #d9fdd3; border-top-right-radius: 0; }
    .msg-received { align-self: flex-start; background: #fff; border-top-left-radius: 0; }

    .chat-input-area { padding: 10px 15px; background: #f0f2f5; display: flex; align-items: center; gap: 10px; }
    .chat-input { flex: 1; border: none; padding: 10px 15px; border-radius: 20px; outline: none; }

    /* Mobile Responsiveness */
    @media (max-width: 768px) {
        .chat-layout { border-radius: 0; border: none; }
        .chat-sidebar { width: 100%; }
        .chat-main { display: none; width: 100%; position: absolute; top: 0; left: 0; height: 100%; z-index: 10; }
        .chat-main.active { display: flex; }
        .back-btn { display: block !important; cursor: pointer; font-size: 1.2rem; color: var(--text-color); }
    }
    .back-btn { display: none; }
    /* WhatsApp-like Styles */
    .chat-layout { display: flex; height: calc(100vh - 140px); background: #fff; border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow-sm); border: 1px solid var(--border-color); }
    .chat-sidebar { width: 350px; border-right: 1px solid var(--border-color); display: flex; flex-direction: column; background: #fff; }
    .chat-main { flex: 1; display: flex; flex-direction: column; background: #efeae2; /* WhatsApp-ish bg */ position: relative; }

    .chat-search { padding: 10px; background: #f0f2f5; border-bottom: 1px solid var(--border-color); }
    .user-list { flex: 1; overflow-y: auto; }

    .user-item {
        display: flex; align-items: center; gap: 15px; padding: 12px 15px; cursor: pointer; border-bottom: 1px solid #f0f2f5; transition: 0.2s;
    }
    .user-item:hover { background: #f5f6f6; }
    .user-item.active { background: #f0f2f5; }

    .avatar { width: 45px; height: 45px; border-radius: 50%; background: #dfe3e5; display: flex; justify-content: center; align-items: center; font-size: 1.2rem; color: #fff; flex-shrink: 0; }

    .chat-header { padding: 10px 15px; background: #f0f2f5; border-bottom: 1px solid var(--border-color); display: flex; align-items: center; gap: 15px; height: 60px; }
    .chat-messages { flex: 1; overflow-y: auto; padding: 20px; display: flex; flex-direction: column; gap: 8px; }

    .message { max-width: 65%; padding: 8px 12px; border-radius: 7.5px; position: relative; font-size: 0.95rem; line-height: 1.4; box-shadow: 0 1px 0.5px rgba(0,0,0,0.13); }
    .msg-sent { align-self: flex-end; background: #d9fdd3; border-top-right-radius: 0; }
    .msg-received { align-self: flex-start; background: #fff; border-top-left-radius: 0; }

    .chat-input-area { padding: 10px 15px; background: #f0f2f5; display: flex; align-items: center; gap: 10px; }
    .chat-input { flex: 1; border: none; padding: 10px 15px; border-radius: 20px; outline: none; }

    /* Mobile Responsiveness */
    @media (max-width: 768px) {
        .chat-layout { border-radius: 0; border: none; }
        .chat-sidebar { width: 100%; }
        .chat-main { display: none; width: 100%; position: absolute; top: 0; left: 0; height: 100%; z-index: 10; }
        .chat-main.active { display: flex; }
        .back-btn { display: block !important; cursor: pointer; font-size: 1.2rem; color: var(--text-color); }
    }
    .back-btn { display: none; }