:root {
  --bg: #0f1115;
  --panel: #171a21;
  --panel-2: #1e222b;
  --line: #2a2f3a;
  --text: #e6e8ec;
  --muted: #8b93a1;
  --accent: #4f8cff;
  --ok: #35c86a;
  --warn: #f0a020;
  --bad: #e5484d;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  height: 100vh;
  overflow: hidden;
}

/* --- Đăng nhập --- */

#login {
  display: grid;
  place-items: center;
  height: 100vh;
  padding: 1rem;
}

.card {
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 2rem;
  max-width: 460px;
  width: 100%;
}

.card h1 { margin: 0 0 .5rem; font-size: 1.8rem; letter-spacing: -.02em; }
.lead { color: var(--muted); line-height: 1.6; margin: 0 0 1.2rem; }

.facts {
  list-style: none;
  padding: 0;
  margin: 0 0 1.5rem;
  font-size: .9rem;
  color: var(--muted);
}
.facts li { padding: .35rem 0 .35rem 1.4rem; position: relative; line-height: 1.5; }
.facts li::before { content: "✓"; position: absolute; left: 0; color: var(--ok); }

button {
  font: inherit;
  cursor: pointer;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: var(--panel-2);
  color: var(--text);
  padding: .55rem .9rem;
}
button:hover { border-color: var(--accent); }

button.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  font-weight: 600;
}
button.primary:hover { filter: brightness(1.1); }
#login-btn { width: 100%; padding: .8rem; }

button.link {
  background: none;
  border: none;
  color: var(--muted);
  padding: .2rem .4rem;
  font-size: .85rem;
}
button.link:hover { color: var(--accent); }

.error { color: var(--bad); font-size: .9rem; min-height: 1.2em; margin: .8rem 0 0; }

input[type=text], input[type=email] {
  font: inherit;
  background: var(--panel-2);
  border: 1px solid var(--line);
  border-radius: 8px;
  color: var(--text);
  padding: .55rem .7rem;
  min-width: 0;
}
input:focus { outline: none; border-color: var(--accent); }

/* --- Bố cục ứng dụng --- */

#app {
  display: grid;
  grid-template-columns: 300px 1fr;
  height: 100vh;
}

aside {
  background: var(--panel);
  border-right: 1px solid var(--line);
  display: grid;
  grid-template-rows: auto auto 1fr auto;
  min-height: 0;
}

.me {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: .5rem;
  padding: 1rem;
  border-bottom: 1px solid var(--line);
}
.me strong { display: block; font-size: .9rem; word-break: break-all; }
.me small { color: var(--muted); font-size: .75rem; }

#add-contact-form {
  display: flex;
  gap: .5rem;
  padding: .8rem 1rem;
  border-bottom: 1px solid var(--line);
}
#add-contact-form input { flex: 1; font-size: .85rem; }

#contacts {
  list-style: none;
  margin: 0;
  padding: .5rem;
  overflow-y: auto;
  min-height: 0;
}

.contact {
  display: flex;
  align-items: center;
  gap: .6rem;
  padding: .6rem .7rem;
  border-radius: 8px;
  cursor: pointer;
}
.contact:hover { background: var(--panel-2); }
.contact.active { background: var(--panel-2); box-shadow: inset 2px 0 0 var(--accent); }
.contact .name { flex: 1; font-size: .9rem; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.dot { width: 9px; height: 9px; border-radius: 50%; flex: none; }
.dot.on { background: var(--ok); }
.dot.off { background: var(--line); }
/* Vòng sáng = đang có kênh P2P trực tiếp */
.dot.p2p { box-shadow: 0 0 0 3px rgba(79, 140, 255, .35); }

.unread:not(:empty) {
  background: var(--accent);
  color: #fff;
  font-size: .7rem;
  border-radius: 10px;
  padding: .05rem .4rem;
  min-width: 1.2rem;
  text-align: center;
}

aside footer { padding: .7rem 1rem; border-top: 1px solid var(--line); }

.status { font-size: .78rem; color: var(--muted); }
.status.ok { color: var(--ok); }
.status.bad { color: var(--warn); }

/* --- Hội thoại --- */

main {
  display: grid;
  grid-template-rows: auto 1fr auto;
  min-height: 0;
}

.conversation {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.2rem;
  border-bottom: 1px solid var(--line);
}

.peer-status { font-size: .78rem; color: var(--muted); margin-top: .2rem; }
.peer-status.p2p { color: var(--ok); }
.peer-status.pending { color: var(--warn); }
.peer-status.offline { color: var(--muted); }

/* Báo khi kết nối bị một tab khác giành mất. Không tự kết nối lại — hai tab
   giành qua giành lại sẽ làm cả hai mất kết nối. */
#replaced-banner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  margin: 1rem 1.2rem 0;
  padding: .8rem 1rem;
  background: rgba(240, 160, 32, .12);
  border: 1px solid var(--warn);
  border-radius: 10px;
  font-size: .88rem;
}
#replaced-banner[hidden] { display: none; }

#messages {
  overflow-y: auto;
  padding: 1.2rem;
  display: flex;
  flex-direction: column;
  gap: .6rem;
  min-height: 0;
}

.msg {
  max-width: min(560px, 75%);
  padding: .55rem .8rem;
  border-radius: 12px;
  background: var(--panel);
  border: 1px solid var(--line);
}
.msg.out { align-self: flex-end; background: #23407a; border-color: #2f4f92; }
.msg .body { white-space: pre-wrap; word-wrap: break-word; line-height: 1.45; }
.msg .meta { font-size: .68rem; color: var(--muted); margin-top: .3rem; }
.msg.out .meta { color: #b9c8e8; }
.msg .file { font-size: .9rem; margin-bottom: .35rem; }
.msg progress { width: 100%; height: 5px; }
.msg .download { font-size: .8rem; color: var(--accent); }

#composer {
  display: flex;
  gap: .6rem;
  align-items: center;
  padding: .9rem 1.2rem;
  border-top: 1px solid var(--line);
}
#composer input[type=text] { flex: 1; }

.attach {
  cursor: pointer;
  font-size: 1.2rem;
  padding: .3rem .5rem;
  border-radius: 8px;
  user-select: none;
}
.attach:hover { background: var(--panel-2); }

#toast {
  position: fixed;
  bottom: 1.2rem;
  left: 50%;
  transform: translateX(-50%);
  background: var(--panel-2);
  border: 1px solid var(--warn);
  color: var(--text);
  padding: .7rem 1.1rem;
  border-radius: 10px;
  font-size: .85rem;
  max-width: 90vw;
  z-index: 10;
}

@media (max-width: 720px) {
  #app { grid-template-columns: 1fr; grid-template-rows: auto 1fr; }
  aside { grid-template-rows: auto auto auto auto; max-height: 45vh; }
}