/* ── Shared Public Shell — Sawasdee Chetupon ─────────────────────────────────
   Canonical shell stylesheet for public pages (teacher.php, learning.php, learning-view.php).
   Load before page-specific <style> blocks.
   ─────────────────────────────────────────────────────────────────────────── */

/* ── Design Tokens ──────────────────────────────────────────────────────────── */
:root {
  --navy:    #0A2558; --navy-dk: #081D45; --navy-xd: #06203d;
  --gold:    #C9A84C; --gold-lt: #E2C97E; --gold-dk: #A6862E;
  --white:   #FFFFFF; --bg:      #EEF1F8; --surface: #FFFFFF;
  --border:  rgba(10,37,88,.09);
  --text-hi: #0D1B3E; --text-mid: #3A4A6B; --text-lo: #7A8AAA;
  --sidebar-w: 256px; --topnav-h: 68px;
  --r-sm: 8px; --r-md: 14px; --r-lg: 20px;
  --shadow-card:  0 2px 16px rgba(10,37,88,.08),0 1px 3px rgba(10,37,88,.06);
  --shadow-hover: 0 10px 40px rgba(10,37,88,.16),0 2px 8px rgba(10,37,88,.10);
  --ease: cubic-bezier(.4,0,.2,1); --dur: .28s;
}

/* ── Reset ──────────────────────────────────────────────────────────────────── */
*,*::before,*::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body {
  font-family: 'K2D', sans-serif;
  background: var(--bg);
  color: var(--text-hi);
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
}

/* ── Sidebar ────────────────────────────────────────────────────────────────── */
#sidebar {
  position: fixed; inset: 0 auto 0 0; width: var(--sidebar-w);
  background:
    repeating-linear-gradient(135deg,rgba(255,255,255,.028) 0px,rgba(255,255,255,.028) 1px,transparent 1px,transparent 22px),
    repeating-linear-gradient(45deg,rgba(255,255,255,.012) 0px,rgba(255,255,255,.012) 1px,transparent 1px,transparent 22px),
    radial-gradient(ellipse 70% 50% at 20% 10%,rgba(201,168,76,.07) 0%,transparent 70%),
    linear-gradient(175deg,var(--navy-dk) 0%,var(--navy) 55%,var(--navy-xd) 100%);
  z-index: 300; display: flex; flex-direction: column;
  box-shadow: 4px 0 24px rgba(0,0,0,.22);
  transition: transform var(--dur) var(--ease);
}
#sidebar::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
  background: linear-gradient(90deg,var(--gold-dk),var(--gold-lt),var(--gold-dk));
}
.sb-header {
  display: flex; align-items: center; gap: 13px;
  padding: 24px 20px 22px; border-bottom: 1px solid rgba(255,255,255,.08); flex-shrink: 0;
}
.sb-logo {
  width: 46px; height: 46px; border-radius: 12px; object-fit: cover;
  border: 2px solid rgba(201,168,76,.45); flex-shrink: 0;
}
.sb-brand-name { font-size: .95rem; font-weight: 700; color: #fff; line-height: 1.25; }
.sb-brand-sub  { font-size: .68rem; font-weight: 300; color: rgba(255,255,255,.40); margin-top: 1px; }
.sb-nav        { flex: 1; overflow-y: auto; padding: 8px 0 16px; }
.sb-nav::-webkit-scrollbar       { width: 3px; }
.sb-nav::-webkit-scrollbar-thumb { background: rgba(255,255,255,.15); border-radius: 2px; }
.sb-section-label {
  font-size: .62rem; font-weight: 600; letter-spacing: .14em;
  text-transform: uppercase; color: rgba(255,255,255,.28); padding: 18px 22px 6px;
}
.sb-item { list-style: none; margin: 1px 10px; }
.sb-link {
  display: flex; align-items: center; gap: 11px; padding: 10px 13px;
  border-radius: var(--r-sm); text-decoration: none; color: rgba(255,255,255,.65);
  font-size: .9rem; font-weight: 400;
  transition: background var(--dur) var(--ease),color var(--dur),transform .12s;
}
.sb-link i { font-size: 1rem; width: 18px; text-align: center; flex-shrink: 0; }
.sb-link:hover { color: #fff; background: rgba(255,255,255,.08); transform: translateX(3px); }
.sb-link.active {
  background: linear-gradient(135deg,rgba(201,168,76,.25),rgba(201,168,76,.10));
  color: var(--gold-lt); font-weight: 600; box-shadow: inset 3px 0 0 var(--gold);
}
.sb-link.active i { color: var(--gold-lt); }
.sb-footer  { padding: 14px 20px; border-top: 1px solid rgba(255,255,255,.07); flex-shrink: 0; }
.sb-version { font-size: .65rem; color: rgba(255,255,255,.22); text-align: center; }

@media(max-width:1023px) {
  #sidebar { transform: translateX(-100%); box-shadow: none; }
  #sidebar.sidebar--open { transform: translateX(0); box-shadow: 6px 0 30px rgba(0,0,0,.35); }
}
@media(min-width:1024px) {
  body.sidebar--collapsed #sidebar    { transform: translateX(calc(-1 * var(--sidebar-w))); }
  body.sidebar--collapsed .main-wrap  { margin-left: 0; }
}

/* ── Sidebar Overlay ────────────────────────────────────────────────────────── */
#sidebar-overlay {
  display: none; position: fixed; inset: 0;
  background: rgba(4,12,36,.55); backdrop-filter: blur(3px);
  z-index: 299; opacity: 0; transition: opacity var(--dur) var(--ease);
}
#sidebar-overlay.overlay--visible { display: block; opacity: 1; }

/* ── Main Wrap ──────────────────────────────────────────────────────────────── */
.main-wrap {
  margin-left: var(--sidebar-w); min-height: 100vh;
  display: flex; flex-direction: column;
  transition: margin-left var(--dur) var(--ease);
}
@media(max-width:1023px) { .main-wrap { margin-left: 0; } }

/* ── Top Nav ────────────────────────────────────────────────────────────────── */
.topnav {
  position: sticky; top: 0; z-index: 200; height: var(--topnav-h);
  background: rgba(255,255,255,.90); backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border); box-shadow: 0 1px 12px rgba(10,37,88,.07);
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 26px; gap: 16px;
}
.topnav-left { display: flex; align-items: center; gap: 14px; min-width: 0; }
.topnav-right { display: flex; align-items: center; gap: 10px; flex-shrink: 0; }
#sidebar-toggle {
  display: flex; align-items: center; justify-content: center;
  width: 40px; height: 40px; border: 1.5px solid var(--border); border-radius: var(--r-sm);
  background: transparent; color: var(--navy); font-size: 1.25rem;
  cursor: pointer; flex-shrink: 0;
  transition: background var(--dur),border-color var(--dur),transform .12s;
}
#sidebar-toggle:hover { background: rgba(10,37,88,.06); border-color: rgba(10,37,88,.18); transform: scale(1.05); }
.topnav-title {
  font-size: 1rem; font-weight: 700; color: var(--navy);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
  display: flex; align-items: center; gap: 8px;
}
.topnav-title i { color: var(--gold-dk); font-size: .95rem; }
.topnav-breadcrumb { font-size: .76rem; color: var(--text-lo); white-space: nowrap; display: none; }
@media(min-width:600px) { .topnav-breadcrumb { display: block; } }

/* ── Scrollbar ──────────────────────────────────────────────────────────────── */
::-webkit-scrollbar        { width: 6px; height: 6px; }
::-webkit-scrollbar-track  { background: transparent; }
::-webkit-scrollbar-thumb  { background: rgba(10,37,88,.18); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: rgba(10,37,88,.30); }