* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #f5f7f8;
  color: #172126;
}
.app {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 320px 1fr;
}
.sidebar {
  background: #102029;
  color: #f7fbfc;
  padding: 18px;
  display: flex;
  flex-direction: column;
  gap: 18px;
}
.brand { display: flex; align-items: center; gap: 12px; }
.mark {
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  background: #32d296;
  color: #102029;
  font-weight: 800;
  border-radius: 8px;
}
h1, h2, p { margin: 0; }
h1 { font-size: 22px; }
#status { color: #9fb3bc; font-size: 13px; margin-top: 3px; }
.panel {
  display: grid;
  gap: 8px;
  padding: 14px;
  border: 1px solid #2f4652;
  border-radius: 8px;
}
label { font-size: 12px; color: #b9c8ce; }
input, button {
  min-height: 40px;
  border-radius: 8px;
  border: 1px solid #cfd8dc;
  padding: 0 12px;
  font: inherit;
}
button {
  border: 0;
  background: #32d296;
  color: #102029;
  font-weight: 700;
  cursor: pointer;
}
nav { display: grid; gap: 8px; }
.conversation {
  width: 100%;
  text-align: left;
  background: transparent;
  color: #f7fbfc;
  border: 1px solid #2f4652;
}
.conversation.active { background: #203540; }
.chat {
  min-width: 0;
  display: grid;
  grid-template-rows: auto 1fr auto;
}
header {
  min-height: 64px;
  padding: 14px 18px;
  border-bottom: 1px solid #dde5e8;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
#logoutBtn {
  background: #e9eff1;
  color: #172126;
}
.messages {
  padding: 18px;
  overflow: auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.msg {
  max-width: min(720px, 86%);
  padding: 10px 12px;
  border-radius: 8px;
  background: #ffffff;
  border: 1px solid #dde5e8;
}
.msg.user {
  align-self: flex-end;
  background: #dff8ec;
  border-color: #b8ebd2;
}
.meta {
  display: block;
  color: #62737b;
  font-size: 12px;
  margin-bottom: 4px;
}
#compose {
  padding: 14px 18px;
  border-top: 1px solid #dde5e8;
  display: grid;
  grid-template-columns: 1fr 110px;
  gap: 10px;
}
@media (max-width: 760px) {
  .app { grid-template-columns: 1fr; }
  .sidebar { min-height: auto; }
  #compose { grid-template-columns: 1fr; }
}