:root {
  --bg: #f5f7fa;
  --card: #ffffff;
  --line: #dde3ea;
  --text: #15202b;
  --muted: #617182;
  --primary: #1d9bf0;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial;
  background: linear-gradient(180deg, #f8fbff 0%, var(--bg) 100%);
  color: var(--text);
}
.app {
  max-width: 860px;
  margin: 0 auto;
  padding: 16px;
  display: grid;
  gap: 14px;
}
.topbar h1 { margin: 0; font-size: 28px; }
.topbar p { margin: 4px 0 0; color: var(--muted); }
.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 14px;
}
form { display: grid; gap: 10px; }
label { display: grid; gap: 6px; font-size: 14px; }
input, textarea, button {
  font: inherit;
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 9px 10px;
}
textarea { min-height: 90px; resize: vertical; }
button {
  cursor: pointer;
  background: var(--primary);
  color: #fff;
  border: none;
}
button:hover { filter: brightness(0.96); }
.status { min-height: 20px; margin: 0; color: var(--muted); }
.timeline-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.tweets { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; }
.tweet {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px;
  background: #fcfdff;
}
.tweet-head { display: flex; justify-content: space-between; gap: 10px; }
.author { font-weight: 700; }
.time { color: var(--muted); font-size: 12px; }
.tweet-text { margin: 8px 0; white-space: pre-wrap; }
.tweet-actions { display: flex; gap: 10px; align-items: center; }
.replies-wrap { margin-top: 8px; }
.replies { list-style: none; margin: 8px 0; padding: 0; display: grid; gap: 6px; }
.replies li { border-left: 2px solid var(--line); padding-left: 8px; font-size: 14px; }
.reply-form {
  display: grid;
  grid-template-columns: 140px 1fr auto;
  gap: 6px;
}
@media (max-width: 700px) {
  .reply-form { grid-template-columns: 1fr; }
}