@import url('https://fonts.googleapis.com/css2?family=Nunito:wght@400;600;700;800&display=swap');

  :root {
    --bg-app: #0b141a;
    --bg-chat: #0b141a;
    --bg-panel: #111b21;
    --bg-input: #1f2c34;
    --bg-msg-out: #005c4b;
    --bg-msg-in: #1f2c34;
    --bg-system: rgba(0,0,0,0.35);
    --text-primary: #e9edef;
    --text-secondary: #8696a0;
    --text-timestamp: #8696a0;
    --accent: #00a884;
    --accent-hover: #00cf9d;
    --border: #2a3942;
    --drop-border: #00a884;
    --shadow: 0 2px 8px rgba(0,0,0,0.4);
    --radius-msg: 8px;
  }

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

  body {
    font-family: 'Nunito', 'Segoe UI', sans-serif;
    background: var(--bg-app);
    color: var(--text-primary);
    height: 100dvh;
    display: flex;
    flex-direction: column;
    overflow: hidden;
  }

  /* ── HEADER ── */
  .app-header {
    background: var(--bg-panel);
    border-bottom: 1px solid var(--border);
    padding: 12px 20px;
    display: flex;
    align-items: center;
    gap: 14px;
    flex-shrink: 0;
    z-index: 10;
  }

  .header-avatar {
    width: 42px; height: 42px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--accent), #128c7e);
    display: flex; align-items: center; justify-content: center;
    font-size: 20px; flex-shrink: 0;
  }

  .header-info { flex: 1; overflow: hidden; }
  .header-name {
    font-size: 16px; font-weight: 700;
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
    color: var(--text-primary);
  }
  .header-sub {
    font-size: 12px; color: var(--text-secondary);
    white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
    margin-top: 1px;
  }

  .btn-new {
    background: var(--bg-input);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    padding: 7px 14px;
    border-radius: 20px;
    font-size: 13px;
    cursor: pointer;
    transition: all .2s;
    white-space: nowrap;
    font-family: inherit;
  }
  .btn-new:hover { border-color: var(--accent); color: var(--accent); }

  /* ── DROP ZONE ── */
  #drop-screen {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 24px;
    padding: 40px 20px;
    background: var(--bg-chat);
  }

  .drop-zone {
    width: 100%; max-width: 440px;
    border: 2px dashed var(--border);
    border-radius: 20px;
    padding: 52px 32px;
    text-align: center;
    cursor: pointer;
    transition: all .25s;
    background: var(--bg-panel);
    position: relative;
  }
  .drop-zone.dragging,
  .drop-zone:hover {
    border-color: var(--drop-border);
    background: rgba(0,168,132,.07);
  }

  .drop-icon {
    font-size: 56px;
    margin-bottom: 16px;
    filter: drop-shadow(0 0 18px rgba(0,168,132,.4));
  }

  .drop-title {
    font-size: 20px; font-weight: 800;
    margin-bottom: 8px;
    color: var(--text-primary);
  }
  .drop-sub {
    font-size: 14px; color: var(--text-secondary);
    line-height: 1.6;
  }

  .btn-upload {
    margin-top: 22px;
    background: var(--accent);
    color: #fff;
    border: none;
    padding: 12px 28px;
    border-radius: 24px;
    font-size: 15px; font-weight: 700;
    cursor: pointer;
    transition: background .2s;
    font-family: inherit;
    display: inline-block;
  }
  .btn-upload:hover { background: var(--accent-hover); }

  #file-input { display: none; }

  .drop-hint {
    font-size: 13px; color: var(--text-secondary);
    text-align: center;
    max-width: 340px;
    line-height: 1.6;
  }

  /* ── CHAT SCREEN ── */
  #chat-screen {
    display: none;
    flex: 1;
    flex-direction: column;
    overflow: hidden;
  }
  #chat-screen.visible { display: flex; }

  /* Wallpaper subtle */
  .chat-body {
    flex: 1;
    overflow-y: auto;
    padding: 16px 20px 24px;
    display: flex;
    flex-direction: column;
    gap: 3px;
    background-color: var(--bg-chat);
    background-image:
      radial-gradient(ellipse at 20% 30%, rgba(0,168,132,.04) 0%, transparent 60%),
      radial-gradient(ellipse at 80% 70%, rgba(18,140,126,.04) 0%, transparent 60%);
    scroll-behavior: smooth;
  }

  /* Scrollbar */
  .chat-body::-webkit-scrollbar { width: 5px; }
  .chat-body::-webkit-scrollbar-track { background: transparent; }
  .chat-body::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

  /* ── DATE SEPARATOR ── */
  .date-sep {
    display: flex; align-items: center;
    justify-content: center;
    margin: 14px 0 10px;
  }
  .date-sep span {
    background: var(--bg-system);
    backdrop-filter: blur(4px);
    color: var(--text-secondary);
    font-size: 12px; font-weight: 600;
    padding: 5px 14px;
    border-radius: 8px;
  }

  /* ── SYSTEM MESSAGE ── */
  .sys-msg {
    display: flex; justify-content: center;
    margin: 6px 0;
  }
  .sys-msg span {
    background: var(--bg-system);
    backdrop-filter: blur(4px);
    color: var(--text-secondary);
    font-size: 12px;
    padding: 5px 14px;
    border-radius: 8px;
    max-width: 80%;
    text-align: center;
    line-height: 1.5;
  }

  /* ── MESSAGE ROW ── */
  .msg-row {
    display: flex;
    align-items: flex-end;
    gap: 6px;
    max-width: 75%;
    animation: fadeUp .18s ease both;
  }
  .msg-row.out { align-self: flex-end; flex-direction: row-reverse; }
  .msg-row.in  { align-self: flex-start; }

  @keyframes fadeUp {
    from { opacity:0; transform: translateY(6px); }
    to   { opacity:1; transform: translateY(0); }
  }

  /* Avatar for group chats */
  .msg-avatar {
    width: 30px; height: 30px;
    border-radius: 50%;
    font-size: 13px; font-weight: 700;
    display: flex; align-items: center; justify-content: center;
    flex-shrink: 0;
    color: #fff;
    margin-bottom: 2px;
  }
  .msg-avatar.hidden { visibility: hidden; }

  /* Bubble */
  .bubble {
    position: relative;
    padding: 7px 10px 6px;
    border-radius: var(--radius-msg);
    max-width: 100%;
    word-break: break-word;
    box-shadow: var(--shadow);
    line-height: 1.45;
  }

  .msg-row.in .bubble {
    background: var(--bg-msg-in);
    border-top-left-radius: 2px;
  }
  .msg-row.out .bubble {
    background: var(--bg-msg-out);
    border-top-right-radius: 2px;
  }

  /* Tail SVG via pseudo */
  .msg-row.in  .bubble::before,
  .msg-row.out .bubble::before {
    content: '';
    position: absolute;
    top: 0;
    width: 8px; height: 13px;
  }
  .msg-row.in .bubble::before {
    left: -7px;
    background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 8 13'%3E%3Cpath fill='%231f2c34' d='M0 0 C3 0 8 5 8 13 L8 0 Z'/%3E%3C/svg%3E") no-repeat;
  }
  .msg-row.out .bubble::before {
    right: -7px;
    background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 8 13'%3E%3Cpath fill='%23005c4b' d='M8 0 C5 0 0 5 0 13 L0 0 Z'/%3E%3C/svg%3E") no-repeat;
  }

  .sender-name {
    font-size: 12.5px; font-weight: 700;
    margin-bottom: 3px;
    display: block;
  }

  .msg-text {
    font-size: 14px;
    color: var(--text-primary);
    white-space: pre-wrap;
  }

  .msg-meta {
    display: flex; align-items: center;
    justify-content: flex-end;
    gap: 4px;
    margin-top: 4px;
    float: right;
    margin-left: 8px;
  }
  .msg-time {
    font-size: 11px;
    color: var(--text-timestamp);
  }

  /* Media omitted */
  .media-omit {
    display: flex; align-items: center; gap: 8px;
    padding: 6px 10px;
    background: rgba(255,255,255,.05);
    border-radius: 6px;
    color: var(--text-secondary);
    font-size: 13px;
    font-style: italic;
  }
  .media-omit span { font-size: 18px; }

  /* Stats bar */
  .stats-bar {
    background: var(--bg-panel);
    border-top: 1px solid var(--border);
    padding: 8px 20px;
    display: flex; gap: 20px; align-items: center;
    font-size: 12px; color: var(--text-secondary);
    flex-shrink: 0;
    overflow-x: auto;
  }
  .stats-bar b { color: var(--accent); font-weight: 700; }

  /* Participants chips */
  .participants {
    display: flex; gap: 6px; flex-wrap: wrap;
    padding: 8px 20px;
    background: var(--bg-panel);
    border-bottom: 1px solid var(--border);
    flex-shrink: 0;
  }
  .chip {
    display: flex; align-items: center; gap: 5px;
    padding: 4px 10px;
    border-radius: 14px;
    font-size: 12px; font-weight: 600;
    background: rgba(255,255,255,.06);
    color: var(--text-primary);
  }
  .chip-dot {
    width: 9px; height: 9px;
    border-radius: 50%;
    flex-shrink: 0;
  }

  /* Loading */
  #loading {
    display: none;
    flex: 1; align-items: center; justify-content: center;
    flex-direction: column; gap: 16px;
    color: var(--text-secondary);
    font-size: 15px;
  }
  #loading.visible { display: flex; }
  .spinner {
    width: 40px; height: 40px;
    border: 3px solid var(--border);
    border-top-color: var(--accent);
    border-radius: 50%;
    animation: spin .8s linear infinite;
  }
  @keyframes spin { to { transform: rotate(360deg); } }

  /* Scroll to bottom btn */
  #scroll-btn {
    position: fixed; bottom: 60px; right: 22px;
    width: 40px; height: 40px;
    border-radius: 50%;
    background: var(--bg-input);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    font-size: 18px;
    display: none;
    align-items: center; justify-content: center;
    cursor: pointer;
    box-shadow: var(--shadow);
    z-index: 20;
    transition: all .2s;
  }
  #scroll-btn:hover { border-color: var(--accent); color: var(--accent); }
  #scroll-btn.visible { display: flex; }

  /* Responsive */
  @media (max-width: 600px) {
    .msg-row { max-width: 88%; }
    .app-header { padding: 10px 14px; }
    .chat-body { padding: 12px 10px 20px; }
  }