:root{
  --bg:#f4f5f7; --card:#fff; --ink:#1a1d24; --muted:#6b7280;
  --line:#e5e7eb; --accent:#4f46e5; --accent-ink:#fff; --good:#16a34a;
  --radius:14px; --shadow:0 1px 3px rgba(0,0,0,.06),0 1px 2px rgba(0,0,0,.04);
}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Inter,sans-serif;
  background:var(--bg);color:var(--ink);line-height:1.5}
a{color:inherit;text-decoration:none}
h1{font-size:1.5rem;margin:.2em 0}
h2{font-size:1.25rem}
.muted{color:var(--muted)}
.small{font-size:.82rem}
.center{text-align:center}
.grow{flex:1}

/* Topbar */
.topbar{display:flex;align-items:center;gap:24px;background:var(--card);
  border-bottom:1px solid var(--line);padding:10px 20px;position:sticky;top:0;z-index:10}
.brand{font-weight:700;font-size:1.1rem}
.topnav{display:flex;gap:18px}
.topnav a{color:var(--muted);font-weight:500}
.topnav a:hover{color:var(--ink)}
.topright{margin-left:auto;display:flex;align-items:center;gap:14px}
.chip{background:#eef2ff;color:var(--accent);font-size:.78rem;font-weight:600;
  padding:3px 9px;border-radius:999px;white-space:nowrap}

/* Layout */
.shell{max-width:1100px;margin:0 auto;display:grid;grid-template-columns:240px 1fr;gap:24px;padding:24px 20px}
.sidebar{position:sticky;top:80px;height:max-content}
.side-label{font-size:.72rem;text-transform:uppercase;letter-spacing:.05em;
  color:var(--muted);margin:14px 6px 6px;font-weight:700}
.side-link{display:flex;justify-content:space-between;align-items:center;
  padding:8px 12px;border-radius:10px;color:#374151;font-weight:500}
.side-link:hover{background:#eceef2}
.lock{opacity:.6}
.content{min-width:0}
.auth-wrap{max-width:400px;margin:8vh auto;padding:0 16px}

/* Cards */
.card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);
  padding:18px;margin-bottom:16px;box-shadow:var(--shadow)}
.flash{background:#ecfdf5;border:1px solid #a7f3d0;color:#065f46;
  padding:10px 14px;border-radius:10px;margin-bottom:16px}
.error{background:#fef2f2;border:1px solid #fecaca;color:#991b1b;
  padding:10px 14px;border-radius:10px;margin-bottom:14px}

/* Forms */
label{display:block;margin:10px 0;font-weight:600;font-size:.9rem}
input,textarea,select{width:100%;padding:10px 12px;border:1px solid var(--line);
  border-radius:10px;font:inherit;margin-top:5px;background:#fff}
textarea{resize:vertical}
.title-input{font-weight:600;border:none;border-bottom:1px solid var(--line);
  border-radius:0;padding-left:0;margin-top:0}
input:focus,textarea:focus{outline:2px solid var(--accent);border-color:transparent}
.btn{display:inline-block;border:none;border-radius:10px;padding:10px 18px;
  font-weight:600;font:600 .95rem inherit;cursor:pointer}
.btn.primary{background:var(--accent);color:var(--accent-ink)}
.btn.primary:hover{filter:brightness(1.08)}
.ghost{background:none;border:none;color:var(--muted);font:600 .9rem inherit;
  cursor:pointer;padding:6px 8px;border-radius:8px}
.ghost:hover{background:#f3f4f6}
.ghost.on{color:var(--accent)}
.inline{display:inline}

/* Avatars */
.avatar{display:inline-grid;place-items:center;width:40px;height:40px;border-radius:50%;
  background:linear-gradient(135deg,#6366f1,#a855f7);color:#fff;font-weight:700;font-size:.85rem}
.avatar.sm{width:30px;height:30px;font-size:.72rem}
.avatar.lg{width:56px;height:56px;font-size:1rem}
.avatar.xl{width:72px;height:72px;font-size:1.3rem}

/* Composer + posts */
.composer-row{display:flex;align-items:center;gap:14px;margin-top:10px}
.schedule-toggle{display:flex;align-items:center;gap:6px;margin:0;font-weight:500;color:var(--muted);cursor:pointer}
.schedule-toggle input{width:auto;margin:0}
#sched-input{width:auto;margin:0}
.composer-row .btn{margin-left:auto}
.feed-head{margin-bottom:8px}
.post-head{display:flex;align-items:center;gap:10px;margin-bottom:10px}
.author{font-weight:600}
.author:hover{text-decoration:underline}
.post-link{display:block;color:inherit}
.post-body{white-space:pre-wrap;word-break:break-word}
.post-foot{display:flex;gap:8px;margin-top:12px;border-top:1px solid var(--line);padding-top:10px}
.pin{color:var(--accent);font-weight:600;font-size:.8rem;margin-bottom:8px}
.back{display:inline-block;color:var(--muted);margin-bottom:12px;font-weight:600}
.comment p{margin:6px 0 0}

/* Leaderboard */
.leaderboard{list-style:none;margin:0;padding:0}
.leaderboard li{display:flex;align-items:center;gap:14px;padding:12px 4px;border-bottom:1px solid var(--line)}
.leaderboard li:last-child{border:none}
.rank{width:26px;text-align:center;font-weight:700;color:var(--muted)}
.rank.medal{color:var(--accent)}
.pts{font-weight:700}

/* Grids */
.member-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(180px,1fr));gap:16px}
.member-card{display:flex;flex-direction:column;align-items:center;text-align:center;gap:8px}
.member-card:hover{border-color:var(--accent)}
.course-card{transition:border-color .15s}
.course-card:hover{border-color:var(--accent)}
.course-card.locked{opacity:.7}
.course-cover{font-size:2.4rem;height:90px;display:grid;place-items:center;
  background:linear-gradient(135deg,#eef2ff,#faf5ff);border-radius:10px;margin-bottom:8px}

/* Profile */
.profile-head{display:flex;align-items:center;gap:18px}
.level-box{text-align:center}
.level-box .big{font-size:2rem;font-weight:800;color:var(--accent);line-height:1}

/* Course player */
.course-layout{display:grid;grid-template-columns:260px 1fr;gap:20px}
.curriculum{border-right:1px solid var(--line);padding-right:8px}
.module{font-weight:700;margin:14px 0 6px;font-size:.9rem}
.lesson-link{display:flex;gap:8px;padding:8px 10px;border-radius:8px;color:#374151}
.lesson-link:hover{background:#f3f4f6}
.lesson-link.active{background:#eef2ff;color:var(--accent);font-weight:600}
.video{position:relative;padding-bottom:56.25%;height:0;margin:14px 0;border-radius:12px;overflow:hidden}
.video iframe{position:absolute;inset:0;width:100%;height:100%;border:0}
.lesson-body{margin:14px 0}
.done-tag{color:var(--good);font-weight:600}

/* Auth */
.auth-card h1{margin-top:0}
.auth-card .btn{width:100%;margin-top:8px}
.big-emoji{font-size:3rem}
.locked-card{max-width:440px;margin:6vh auto}

@media(max-width:780px){
  .shell{grid-template-columns:1fr}
  .sidebar{position:static}
  .course-layout{grid-template-columns:1fr}
  .curriculum{border:none;border-bottom:1px solid var(--line);padding-bottom:8px}
  .topnav{display:none}
}