:root {
    --bg-dark: #0f172a;
    --bg-card: #1e293b;
    --bg-sidebar: #111827;
    --bg-chat: #0b0f19;
    --bg-input: #1e293b;
    --accent-color: #6366f1;
    --accent-hover: #4f46e5;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --border-color: #334155;
    --msg-sent: #4f46e5;
    --msg-received: #1e293b;
  }
  
  * {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', sans-serif;
  }
  
  body {
    background-color: var(--bg-dark);
    color: var(--text-main);
    height: 100vh;
    overflow: hidden;
  }
  
  /* Utils */
  .hidden { display: none !important; }
  
  /* ================= AUTENTICAÇÃO ================= */
  .auth-container {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    background: radial-gradient(circle at top, #1e1b4b 0%, #0f172a 100%);
    padding: 20px;
  }
  
  .auth-card {
    background-color: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    width: 100%;
    max-width: 420px;
    padding: 32px;
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.5);
  }
  
  .auth-header {
    text-align: center;
    margin-bottom: 24px;
  }
  
  .brand-logo {
    font-size: 40px;
    color: var(--accent-color);
    margin-bottom: 8px;
  }
  
  .auth-header h2 {
    font-size: 24px;
    font-weight: 700;
  }
  
  .auth-header p {
    color: var(--text-muted);
    font-size: 14px;
    margin-top: 4px;
  }
  
  .auth-tabs {
    display: flex;
    background-color: var(--bg-dark);
    padding: 4px;
    border-radius: 8px;
    margin-bottom: 24px;
  }
  
  .tab-btn {
    flex: 1;
    background: none;
    border: none;
    color: var(--text-muted);
    padding: 10px;
    font-weight: 500;
    cursor: pointer;
    border-radius: 6px;
    transition: all 0.2s;
  }
  
  .tab-btn.active {
    background-color: var(--accent-color);
    color: #fff;
  }
  
  .auth-form {
    display: flex;
    flex-direction: column;
    gap: 16px;
  }
  
  .input-group label {
    display: block;
    font-size: 12px;
    font-weight: 600;
    color: var(--text-muted);
    margin-bottom: 6px;
    text-transform: uppercase;
  }
  
  .input-wrapper {
    display: flex;
    align-items: center;
    background-color: var(--bg-dark);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0 12px;
  }
  
  .input-wrapper i {
    color: var(--text-muted);
    margin-right: 8px;
  }
  
  .input-wrapper input {
    width: 100%;
    background: none;
    border: none;
    padding: 12px 0;
    color: var(--text-main);
    outline: none;
    font-size: 14px;
  }
  
  .btn-primary {
    background-color: var(--accent-color);
    color: #fff;
    border: none;
    padding: 12px;
    border-radius: 8px;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
    margin-top: 8px;
  }
  
  .btn-primary:hover {
    background-color: var(--accent-hover);
  }
  
  .auth-error {
    margin-top: 16px;
    background-color: rgba(239, 68, 68, 0.1);
    border: 1px solid #ef4444;
    color: #f87171;
    padding: 10px;
    border-radius: 8px;
    font-size: 13px;
    text-align: center;
  }
  
  /* ================= INTERFACE DO APP ================= */
  .app-container {
    display: flex;
    height: 100vh;
    width: 100vw;
  }
  
  /* Sidebar */
  .sidebar {
    width: 360px;
    background-color: var(--bg-sidebar);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
  }
  
  .sidebar-header {
    padding: 16px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid var(--border-color);
  }
  
  .user-profile-summary {
    display: flex;
    align-items: center;
    gap: 12px;
  }
  
  .avatar {
    width: 42px;
    height: 42px;
    border-radius: 50%;
    background-color: var(--accent-color);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 16px;
    text-transform: uppercase;
  }
  
  .user-info h3 {
    font-size: 15px;
    font-weight: 600;
  }
  
  .user-id-badge {
    font-size: 12px;
    color: var(--text-muted);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 4px;
    margin-top: 2px;
  }
  
  .user-id-badge strong {
    color: var(--accent-color);
    letter-spacing: 1px;
  }
  
  .btn-icon {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 20px;
    cursor: pointer;
    padding: 6px;
    border-radius: 6px;
  }
  
  .btn-icon:hover {
    color: var(--text-main);
    background-color: var(--bg-card);
  }
  
  /* Adicionar Contato Box */
  .add-contact-box {
    padding: 16px;
    border-bottom: 1px solid var(--border-color);
  }
  
  .add-contact-box .input-wrapper button {
    background: var(--accent-color);
    border: none;
    color: #fff;
    padding: 6px 12px;
    border-radius: 6px;
    cursor: pointer;
  }
  
  /* Lista de Chats */
  .chats-list {
    flex: 1;
    overflow-y: auto;
  }
  
  .empty-state-sidebar {
    padding: 40px 20px;
    text-align: center;
    color: var(--text-muted);
  }
  
  .empty-state-sidebar i {
    font-size: 48px;
    margin-bottom: 12px;
    opacity: 0.5;
  }
  
  .chat-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    cursor: pointer;
    border-bottom: 1px solid rgba(255, 255, 255, 0.03);
    transition: background 0.2s;
  }
  
  .chat-item:hover, .chat-item.active {
    background-color: var(--bg-card);
  }
  
  .chat-item-info {
    flex: 1;
    overflow: hidden;
  }
  
  .chat-item-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: 4px;
  }
  
  .chat-item-name {
    font-size: 14px;
    font-weight: 600;
  }
  
  .chat-item-lastmsg {
    font-size: 13px;
    color: var(--text-muted);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
  }
  
  /* Área Principal do Chat */
  .chat-main {
    flex: 1;
    background-color: var(--bg-chat);
    display: flex;
    flex-direction: column;
  }
  
  .no-chat-container {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 20px;
  }
  
  .welcome-box i {
    font-size: 64px;
    color: var(--accent-color);
    margin-bottom: 16px;
  }
  
  .welcome-box h2 {
    font-size: 24px;
    margin-bottom: 8px;
  }
  
  .welcome-box p {
    color: var(--text-muted);
    max-width: 400px;
  }
  
  .active-chat-wrapper {
    display: flex;
    flex-direction: column;
    height: 100%;
  }
  
  .chat-header {
    padding: 16px 24px;
    background-color: var(--bg-sidebar);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
  }
  
  .active-contact-info {
    display: flex;
    align-items: center;
    gap: 12px;
  }
  
  .status-indicator {
    font-size: 12px;
    color: var(--text-muted);
  }
  
  .messages-container {
    flex: 1;
    padding: 24px;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 12px;
  }
  
  /* Balões de Mensagem */
  .message-bubble {
    max-width: 60%;
    padding: 10px 14px;
    border-radius: 12px;
    font-size: 14px;
    line-height: 1.4;
    word-break: break-word;
    position: relative;
  }
  
  .message-bubble.sent {
    align-self: flex-end;
    background-color: var(--msg-sent);
    color: #fff;
    border-bottom-right-radius: 2px;
  }
  
  .message-bubble.received {
    align-self: flex-start;
    background-color: var(--msg-received);
    color: var(--text-main);
    border-bottom-left-radius: 2px;
    border: 1px solid var(--border-color);
  }
  
  .message-time {
    font-size: 10px;
    opacity: 0.7;
    margin-top: 4px;
    text-align: right;
    display: block;
  }
  
  .chat-footer {
    padding: 16px 24px;
    background-color: var(--bg-sidebar);
    border-top: 1px solid var(--border-color);
  }
  
  .chat-footer form {
    display: flex;
    gap: 12px;
  }
  
  .chat-footer input {
    flex: 1;
    background-color: var(--bg-dark);
    border: 1px solid var(--border-color);
    border-radius: 24px;
    padding: 12px 20px;
    color: var(--text-main);
    outline: none;
  }
  
  .btn-send {
    background-color: var(--accent-color);
    border: none;
    color: #fff;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 18px;
  }