/* ===== MATEMATIKA 4 — Colorful Edition ===== */
:root {
  --bg: #080e1f;
  --card: #0e1a35;
  --card-2: #162040;
  --primary: #ffb020;
  --primary-2: #ff6b00;
  --accent: #4cc9f0;
  --green: #34d399;
  --red: #f87171;
  --pink: #f472b6;
  --violet: #a78bfa;
  --teal: #2dd4bf;
  --text: #f1f5f9;
  --muted: #94a3b8;
  --shadow: 0 10px 30px -10px rgba(0,0,0,0.7);
  --radius: 16px;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }

body {
  font-family: "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  line-height: 1.5;
  overflow-x: hidden;
}

/* animated gradient aurora behind everything */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  background:
    radial-gradient(ellipse 800px 500px at 20% 0%,   rgba(99,40,255,0.18)  0%, transparent 70%),
    radial-gradient(ellipse 700px 400px at 80% 10%,  rgba(255,80,120,0.12) 0%, transparent 70%),
    radial-gradient(ellipse 600px 500px at 10% 90%,  rgba(0,200,200,0.10)  0%, transparent 70%),
    radial-gradient(ellipse 900px 600px at 90% 80%,  rgba(80,120,255,0.10) 0%, transparent 70%);
  animation: auroraShift 12s ease-in-out infinite alternate;
}

@keyframes auroraShift {
  0%   { opacity: 1; transform: scale(1); }
  100% { opacity: 0.7; transform: scale(1.08) translateY(-20px); }
}

body > *:not(#mathbg) { position: relative; z-index: 1; }

h1, h2, h3 { margin: 0; font-weight: 800; letter-spacing: -0.02em; }

/* ===== TOPBAR ===== */
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 16px;
  padding: 16px clamp(16px, 4vw, 40px);
  background: linear-gradient(90deg,
    rgba(99,40,255,0.18) 0%,
    rgba(255,80,120,0.12) 50%,
    rgba(0,200,200,0.12) 100%);
  border-bottom: 1px solid rgba(255,255,255,0.10);
  backdrop-filter: blur(8px);
}

.brand { display: flex; align-items: center; gap: 14px; }

/* rainbow animated title */
.brand h1 {
  font-size: 24px;
  background: linear-gradient(90deg,
    #ff6b6b, #ffd93d, #6bcb77, #4cc9f0, #a78bfa, #f472b6, #ff6b6b);
  background-size: 300% 100%;
  -webkit-background-clip: text; background-clip: text; color: transparent;
  animation: rainbowFlow 4s linear infinite;
}

@keyframes rainbowFlow {
  0%   { background-position: 0% 50%; }
  100% { background-position: 300% 50%; }
}

.brand .tag { margin: 2px 0 0; color: var(--muted); font-size: 13px; }

.logo {
  width: 46px; height: 46px; border-radius: 14px;
  display: grid; place-items: center;
  background: linear-gradient(135deg, #a78bfa, #f472b6, #ffb020);
  background-size: 200% 200%;
  color: #fff; font-weight: 900; font-size: 26px;
  box-shadow: 0 0 0 3px rgba(167,139,250,0.3), var(--shadow);
  animation: logoPulse 3s ease-in-out infinite;
}

@keyframes logoPulse {
  0%,100% { box-shadow: 0 0 0 3px rgba(167,139,250,0.3), 0 0 20px rgba(167,139,250,0.4); }
  50%      { box-shadow: 0 0 0 5px rgba(244,114,182,0.4), 0 0 30px rgba(244,114,182,0.5); }
}

/* ===== STATS ===== */
.stats { display: flex; gap: 8px; flex-wrap: wrap; align-items: center; }

.stat {
  border-radius: 12px;
  padding: 7px 13px; min-width: 68px;
  display: flex; flex-direction: column; align-items: center;
  position: relative; overflow: hidden;
  border: 1px solid rgba(255,255,255,0.08);
  background: rgba(255,255,255,0.05);
  backdrop-filter: blur(6px);
}
.stat .label { font-size: 10px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.07em; }
.stat span:last-child { font-size: 20px; font-weight: 900; }
.stat.xp    { border-color: rgba(255,176,32,0.35); }
.stat.ok    { border-color: rgba(52,211,153,0.35); }
.stat.fail  { border-color: rgba(248,113,113,0.35); }
.stat.streak{ border-color: rgba(76,201,240,0.35); }
.stat.xp    span:last-child { color: var(--primary);  text-shadow: 0 0 12px rgba(255,176,32,0.6); }
.stat.ok    span:last-child { color: var(--green);    text-shadow: 0 0 12px rgba(52,211,153,0.6); }
.stat.fail  span:last-child { color: var(--red);      text-shadow: 0 0 12px rgba(248,113,113,0.6); }
.stat.streak span:last-child{ color: var(--accent);   text-shadow: 0 0 12px rgba(76,201,240,0.6); }

/* user menu */
.user-menu {
  display: flex; flex-direction: column; align-items: center; gap: 4px;
  padding: 6px 12px;
}
.user-name {
  font-size: 12px; color: var(--accent); font-weight: 700;
  max-width: 130px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.logout-btn {
  font-size: 12px; color: var(--muted); text-decoration: none;
  padding: 4px 10px; border-radius: 8px;
  border: 1px solid rgba(255,255,255,0.08);
  background: rgba(255,255,255,0.03);
  transition: all 0.2s;
}
.logout-btn:hover { color: var(--red); border-color: rgba(248,113,113,0.5); }

/* ===== TROPHIES ===== */
.trophies { display: flex; gap: 4px; align-items: center; }
.trophy {
  font-size: 28px; display: grid; place-items: center;
  padding: 0 4px; cursor: default; user-select: none;
  animation: trophyPop .9s ease both, trophyShine 2.4s ease-in-out infinite;
}
.trophy.tier-bronze { filter: drop-shadow(0 0 6px rgba(255,176,32,0.7)); }
.trophy.tier-gold   { filter: drop-shadow(0 0 8px rgba(255,215,0,0.8)); font-size: 30px; }
.trophy.tier-crown  { filter: drop-shadow(0 0 10px rgba(244,114,182,0.8)); font-size: 32px; }
@keyframes trophyPop {
  0%   { transform: scale(0) rotate(-30deg); opacity: 0; }
  60%  { transform: scale(1.3) rotate(8deg); opacity: 1; }
  100% { transform: scale(1) rotate(0); }
}
@keyframes trophyShine {
  0%,100% { filter: drop-shadow(0 0 4px rgba(255,215,0,.5)); }
  50%      { filter: drop-shadow(0 0 16px rgba(255,215,0,1)); }
}

.trophy-toast {
  position: fixed; left: 50%; top: 24px; transform: translateX(-50%);
  background: linear-gradient(135deg, #2a0a3a, #1a1550);
  border: 1px solid rgba(167,139,250,0.6);
  color: #c4b5fd;
  padding: 14px 22px; border-radius: 16px;
  font-weight: 800; font-size: 16px;
  box-shadow: 0 12px 40px rgba(0,0,0,0.6), 0 0 30px rgba(167,139,250,0.3);
  z-index: 1000;
  display: flex; align-items: center; gap: 12px;
  animation: toastIn .35s ease both;
}
.trophy-toast .icon { font-size: 36px; }
.trophy-toast.out { animation: toastOut .4s ease both; }
@keyframes toastIn  { from { opacity:0; transform:translate(-50%,-20px); } to { opacity:1; transform:translate(-50%,0); } }
@keyframes toastOut { from { opacity:1; transform:translate(-50%,0); } to { opacity:0; transform:translate(-50%,-20px); } }

.error-toast {
  position: fixed; left: 50%; top: 24px; transform: translateX(-50%);
  background: linear-gradient(135deg, #3a0a0a, #2a1515);
  border: 1px solid rgba(248,113,113,0.6);
  color: #fca5a5;
  padding: 14px 22px; border-radius: 16px;
  font-weight: 600; font-size: 15px;
  box-shadow: 0 12px 40px rgba(0,0,0,0.6), 0 0 30px rgba(248,113,113,0.2);
  z-index: 1000;
  display: flex; align-items: center; gap: 12px;
  animation: toastIn .35s ease both;
}
.error-toast .icon { font-size: 24px; }
.error-toast.out { animation: toastOut .4s ease both; }

/* ===== LAYOUT ===== */
main { max-width: 980px; margin: 0 auto; padding: clamp(16px,4vw,36px); }

.screen { display: none; animation: fadeUp .3s ease; }
.screen.active { display: block; }
@keyframes fadeUp { from { opacity:0; transform:translateY(14px); } to { opacity:1; transform:none; } }

.screen h2 {
  margin-bottom: 20px;
  font-size: clamp(22px, 3vw, 30px);
  background: linear-gradient(90deg, var(--accent), var(--violet), var(--pink));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}

.back {
  background: transparent; color: var(--muted); border: none; cursor: pointer;
  font-size: 14px; padding: 4px 0 12px; margin-bottom: 4px; transition: color .15s;
}
.back:hover { color: var(--accent); }

/* ===== TOPIC TILES — each gets a color ===== */
.grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 14px;
}
.grid.small { grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); }

/* color palette cycling via nth-child */
.tile {
  border-radius: var(--radius);
  padding: 20px; cursor: pointer; text-align: left;
  color: var(--text); font: inherit;
  transition: transform .18s ease, box-shadow .18s ease;
  display: flex; flex-direction: column; gap: 10px;
  position: relative; overflow: hidden;
  border: 1px solid rgba(255,255,255,0.10);
  background: linear-gradient(160deg, var(--card), var(--card-2));
}

/* animated shimmer on hover */
.tile::before {
  content: "";
  position: absolute; inset: 0;
  background: linear-gradient(120deg, transparent 0%, rgba(255,255,255,0.06) 50%, transparent 100%);
  transform: translateX(-100%);
  transition: transform .4s ease;
}
.tile:hover::before { transform: translateX(100%); }

.tile:nth-child(7n+1) { border-top: 3px solid #f472b6; }
.tile:nth-child(7n+2) { border-top: 3px solid #60a5fa; }
.tile:nth-child(7n+3) { border-top: 3px solid #34d399; }
.tile:nth-child(7n+4) { border-top: 3px solid #fbbf24; }
.tile:nth-child(7n+5) { border-top: 3px solid #a78bfa; }
.tile:nth-child(7n+6) { border-top: 3px solid #2dd4bf; }
.tile:nth-child(7n+0) { border-top: 3px solid #fb923c; }

.tile:nth-child(7n+1):hover { box-shadow: 0 0 0 1px #f472b6, 0 16px 40px -12px rgba(244,114,182,.45); }
.tile:nth-child(7n+2):hover { box-shadow: 0 0 0 1px #60a5fa, 0 16px 40px -12px rgba(96,165,250,.45); }
.tile:nth-child(7n+3):hover { box-shadow: 0 0 0 1px #34d399, 0 16px 40px -12px rgba(52,211,153,.45); }
.tile:nth-child(7n+4):hover { box-shadow: 0 0 0 1px #fbbf24, 0 16px 40px -12px rgba(251,191,36,.45); }
.tile:nth-child(7n+5):hover { box-shadow: 0 0 0 1px #a78bfa, 0 16px 40px -12px rgba(167,139,250,.45); }
.tile:nth-child(7n+6):hover { box-shadow: 0 0 0 1px #2dd4bf, 0 16px 40px -12px rgba(45,212,191,.45); }
.tile:nth-child(7n+0):hover { box-shadow: 0 0 0 1px #fb923c, 0 16px 40px -12px rgba(251,146,60,.45); }

.tile:hover { transform: translateY(-4px) scale(1.02); }
.tile h3 { font-size: 16px; }
.tile p  { margin: 0; color: var(--muted); font-size: 13px; }

.tile .ico {
  width: 38px; height: 38px; border-radius: 10px;
  display: grid; place-items: center; font-size: 17px; font-weight: 900;
}
.tile:nth-child(7n+1) .ico { background: rgba(244,114,182,.15); color: #f472b6; }
.tile:nth-child(7n+2) .ico { background: rgba(96,165,250,.15);  color: #60a5fa; }
.tile:nth-child(7n+3) .ico { background: rgba(52,211,153,.15);  color: #34d399; }
.tile:nth-child(7n+4) .ico { background: rgba(251,191,36,.15);  color: #fbbf24; }
.tile:nth-child(7n+5) .ico { background: rgba(167,139,250,.15); color: #a78bfa; }
.tile:nth-child(7n+6) .ico { background: rgba(45,212,191,.15);  color: #2dd4bf; }
.tile:nth-child(7n+0) .ico { background: rgba(251,146,60,.15);  color: #fb923c; }

/* ===== DIFFICULTY BUTTONS ===== */
.diff-row { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; flex-wrap: wrap; }
.diff-label { color: var(--muted); font-size: 14px; }
.diff-buttons { display: flex; gap: 8px; flex-wrap: wrap; }

.diff {
  background: rgba(255,255,255,0.05); color: var(--text);
  border: 1px solid rgba(255,255,255,0.10);
  padding: 8px 18px; border-radius: 999px; cursor: pointer;
  font: inherit; font-size: 13px; font-weight: 600;
  transition: all .18s ease;
}
.diff:hover { background: rgba(255,255,255,0.10); transform: translateY(-1px); }
.diff[data-diff="easy"].active  { background: linear-gradient(135deg,#34d399,#059669); border-color: transparent; color:#052e16; }
.diff[data-diff="medium"].active{ background: linear-gradient(135deg,#fbbf24,#f59e0b); border-color: transparent; color:#451a03; }
.diff[data-diff="hard"].active  { background: linear-gradient(135deg,#f87171,#dc2626); border-color: transparent; color:#fff; }

/* ===== BUTTONS ===== */
.primary {
  background: linear-gradient(135deg, #a78bfa, #7c3aed);
  color: #fff; border: none; cursor: pointer;
  padding: 11px 20px; border-radius: 12px;
  font: inherit; font-weight: 700; font-size: 14px;
  transition: transform .12s ease, box-shadow .12s ease;
  box-shadow: 0 6px 20px -6px rgba(124,58,237,0.6);
  position: relative; overflow: hidden;
}
.primary::after {
  content: "";
  position: absolute; inset: 0;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.15), transparent);
  transform: translateX(-100%);
  transition: transform .45s ease;
}
.primary:hover::after { transform: translateX(100%); }
.primary:hover { transform: translateY(-2px); box-shadow: 0 10px 28px -6px rgba(124,58,237,0.75); }
.primary.big { padding: 14px 24px; font-size: 16px; margin-top: 18px; }

#examBtn {
  background: linear-gradient(135deg, #f472b6, #db2777);
  box-shadow: 0 6px 20px -6px rgba(219,39,119,0.6);
}
#examBtn:hover { box-shadow: 0 10px 28px -6px rgba(219,39,119,0.75); }

#randomFromTopic {
  background: linear-gradient(135deg, #2dd4bf, #0d9488);
  box-shadow: 0 6px 20px -6px rgba(13,148,136,0.6);
}

.primary.ghost {
  background: transparent; color: var(--text);
  border: 1px solid rgba(255,255,255,0.18);
  box-shadow: none;
}
.primary.ghost:hover { background: rgba(255,255,255,0.07); }

/* ===== CHIPS ===== */
.task-meta { display: flex; gap: 8px; flex-wrap: wrap; margin: 8px 0 16px; }
.chip {
  background: rgba(255,255,255,0.06); color: var(--muted);
  border: 1px solid rgba(255,255,255,0.08);
  padding: 4px 14px; border-radius: 999px; font-size: 12px; font-weight: 600;
}
.diff-chip { color: var(--accent); border-color: rgba(76,201,240,0.25); }
.xp-chip   { color: var(--primary); border-color: rgba(255,176,32,0.3); }

/* ===== TASK CARD ===== */
.task-card {
  background: linear-gradient(160deg, var(--card), var(--card-2));
  border: 1px solid rgba(255,255,255,0.09);
  border-radius: 20px;
  padding: clamp(18px,4vw,32px);
  box-shadow: var(--shadow);
  position: relative; overflow: hidden;
}
.task-card::before {
  content: "";
  position: absolute; top: 0; left: 0; right: 0; height: 3px;
  background: linear-gradient(90deg, #a78bfa, #f472b6, #fbbf24, #34d399, #4cc9f0);
  background-size: 200% 100%;
  animation: topBarFlow 3s linear infinite;
}
@keyframes topBarFlow {
  0%   { background-position: 0% 0%; }
  100% { background-position: 200% 0%; }
}

.question {
  font-size: clamp(18px,2.6vw,22px); font-weight: 600;
  line-height: 1.55; margin: 0 0 14px;
  white-space: pre-wrap; font-family: inherit;
  color: var(--text);
}

.hint { margin: 0 0 18px; color: var(--teal); font-size: 13px; font-style: italic; }

.answer-row { display: flex; gap: 10px; flex-wrap: wrap; }
.answer-row input {
  flex: 1 1 200px; min-width: 0;
  padding: 14px 16px; font-size: 17px; font-weight: 600;
  background: rgba(0,0,0,0.3); color: var(--text);
  border: 2px solid rgba(255,255,255,0.08); border-radius: 12px;
  outline: none; transition: border-color .2s, box-shadow .2s;
}
.answer-row input:focus {
  border-color: var(--violet);
  box-shadow: 0 0 0 4px rgba(167,139,250,0.2);
}

/* ===== FEEDBACK ===== */
.feedback { margin-top: 22px; }
.feedback.hidden { display: none; }

.result {
  display: flex; align-items: center; gap: 12px;
  font-size: 20px; font-weight: 800;
  animation: resultPop .35s cubic-bezier(.34,1.56,.64,1) both;
}
@keyframes resultPop { from { transform: scale(0.7); opacity: 0; } to { transform: scale(1); opacity: 1; } }

.result .icon {
  width: 36px; height: 36px; border-radius: 50%;
  display: grid; place-items: center; font-size: 20px; font-weight: 900;
}
.result.correct .icon { background: rgba(52,211,153,.2); color: var(--green); box-shadow: 0 0 12px rgba(52,211,153,.5); }
.result.wrong   .icon { background: rgba(248,113,113,.2); color: var(--red);   box-shadow: 0 0 12px rgba(248,113,113,.5); }
.result.correct { color: var(--green); text-shadow: 0 0 16px rgba(52,211,153,.4); }
.result.wrong   { color: var(--red);   text-shadow: 0 0 16px rgba(248,113,113,.4); }

.correct-line { color: var(--muted); margin: 10px 0; }
.correct-line strong { color: var(--text); }

/* ===== ANSWER COMPARE ===== */
.answer-compare {
  display: flex; gap: 10px; flex-wrap: wrap; margin: 14px 0 4px;
}
.answer-yours, .answer-correct {
  display: flex; flex-direction: column; gap: 4px;
  padding: 10px 16px; border-radius: 12px; flex: 1; min-width: 110px;
}
.answer-yours  { background: rgba(248,113,113,0.08); border: 1px solid rgba(248,113,113,0.25); }
.answer-correct{ background: rgba(52,211,153,0.08);  border: 1px solid rgba(52,211,153,0.25);  }
.ans-label { font-size: 10px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.07em; }
.answer-yours  strong { color: var(--red);   font-size: 18px; font-weight: 900; }
.answer-correct strong { color: var(--green); font-size: 18px; font-weight: 900; }

/* ===== EXPLANATION PANEL ===== */
.explanation-panel {
  border-radius: 14px; padding: 14px 18px; margin-top: 10px;
  border: 1px solid rgba(76,201,240,0.15);
  background: rgba(0,0,0,0.2);
  transition: border-color .2s, background .2s;
}
.explanation-panel.hidden { display: none; }
.explanation-panel.wrong-mode {
  border: 1px solid rgba(251,191,36,0.4);
  border-left: 4px solid #fbbf24;
  background: rgba(251,191,36,0.04);
}
.explanation-panel.correct-mode {
  border: 1px solid rgba(52,211,153,0.2);
  border-left: 4px solid #34d399;
  background: rgba(52,211,153,0.03);
}
.expl-title {
  font-weight: 700; font-size: 12px; color: var(--accent);
  margin-bottom: 12px; display: flex; align-items: center; gap: 6px;
  text-transform: uppercase; letter-spacing: 0.06em;
}
.explanation-panel.wrong-mode  .expl-title { color: #fbbf24; }
.explanation-panel.correct-mode .expl-title { color: var(--green); }
.expl-steps { display: flex; flex-direction: column; gap: 7px; }
.expl-step {
  display: flex; align-items: flex-start; gap: 10px;
  animation: stepIn .22s ease both;
}
.expl-step:nth-child(1){ animation-delay:.04s; }
.expl-step:nth-child(2){ animation-delay:.09s; }
.expl-step:nth-child(3){ animation-delay:.14s; }
.expl-step:nth-child(4){ animation-delay:.19s; }
.expl-step:nth-child(5){ animation-delay:.24s; }
@keyframes stepIn { from { opacity:0; transform:translateX(-8px); } to { opacity:1; transform:none; } }
.step-num {
  min-width: 22px; height: 22px; border-radius: 50%;
  background: rgba(167,139,250,0.18); color: var(--violet);
  display: grid; place-items: center;
  font-size: 11px; font-weight: 800; flex-shrink: 0; margin-top: 2px;
}
.explanation-panel.wrong-mode  .step-num { background: rgba(251,191,36,0.15); color: #fbbf24; }
.explanation-panel.correct-mode .step-num { background: rgba(52,211,153,0.15); color: var(--green); }
.step-text {
  color: var(--text); font-size: 14px; line-height: 1.55;
  font-family: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  white-space: pre-wrap;
}

/* ===== HOME HEAD ===== */
.home-head {
  display: flex; justify-content: space-between; align-items: center;
  gap: 12px; margin-bottom: 20px; flex-wrap: wrap;
}

/* ===== EXAM BAR ===== */
.exam-bar { display: flex; gap: 8px; flex-wrap: wrap; margin: 8px 0 18px; }

/* ===== RESULT CARD ===== */
.result-card {
  background: linear-gradient(160deg, var(--card), var(--card-2));
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 20px; padding: clamp(20px,4vw,34px);
  box-shadow: var(--shadow);
  position: relative; overflow: hidden;
}
.result-card::before {
  content: "";
  position: absolute; top: 0; left: 0; right: 0; height: 4px;
  background: linear-gradient(90deg, #f472b6, #a78bfa, #4cc9f0, #34d399, #fbbf24);
}

.grade-big { font-size: 22px; margin-bottom: 12px; font-weight: 700; }
.grade-big span {
  font-size: 64px; font-weight: 900;
  background: linear-gradient(135deg, #fbbf24, #f472b6, #a78bfa);
  -webkit-background-clip: text; background-clip: text; color: transparent;
  margin-left: 8px; display: inline-block;
  animation: gradeFloat 2s ease-in-out infinite;
}
@keyframes gradeFloat {
  0%,100% { transform: translateY(0); }
  50%      { transform: translateY(-5px); }
}

.grade-verdict { margin: 6px 0 16px; font-size: 18px; font-weight: 700; text-align: center; }
.grade-verdict.bad   { color: var(--red); }
.grade-verdict.mid   { color: var(--accent); }
.grade-verdict.good  { color: var(--green); }
.grade-verdict.great {
  background: linear-gradient(90deg, #fbbf24, #f472b6, #a78bfa);
  -webkit-background-clip: text; background-clip: text; color: transparent;
  animation: rainbowFlow 2s linear infinite;
}

.result-line { margin: 7px 0; color: var(--muted); font-size: 15px; }
.result-line strong { color: var(--text); }
.section-h { margin: 20px 0 10px; font-size: 16px; color: var(--violet); font-weight: 700; }

.topic-stats { display: grid; grid-template-columns: 1fr; gap: 6px; }
.topic-stats .row {
  display: flex; justify-content: space-between;
  background: rgba(255,255,255,0.04); padding: 9px 14px; border-radius: 10px;
  font-size: 14px; border: 1px solid rgba(255,255,255,0.06);
}
.topic-stats .row .ok  { color: var(--green); font-weight: 800; }
.topic-stats .row .bad { color: var(--red);   font-weight: 800; }

.result-actions { display: flex; gap: 10px; margin-top: 22px; flex-wrap: wrap; }

#resRetry {
  background: linear-gradient(135deg, #34d399, #059669);
  box-shadow: 0 6px 20px -6px rgba(5,150,105,0.6);
}

/* ===== GRADE GRID ===== */
.grade-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 16px;
}

.grade-tile {
  border-radius: 20px;
  padding: 24px 20px;
  cursor: pointer;
  text-align: center;
  color: var(--text);
  font: inherit;
  border: 1px solid rgba(255,255,255,0.10);
  display: flex; flex-direction: column; align-items: center; gap: 6px;
  position: relative; overflow: hidden;
  transition: transform .2s ease, box-shadow .2s ease;
  background: linear-gradient(160deg, var(--card), var(--card-2));
}

.grade-tile::before {
  content: "";
  position: absolute; inset: 0;
  background: linear-gradient(120deg, transparent 0%, rgba(255,255,255,0.06) 50%, transparent 100%);
  transform: translateX(-100%);
  transition: transform .4s ease;
}
.grade-tile:hover::before { transform: translateX(100%); }

/* rainbow borders by grade number */
.grade-tile:nth-child(8n+1) { border-top: 4px solid #f472b6; }
.grade-tile:nth-child(8n+2) { border-top: 4px solid #fb923c; }
.grade-tile:nth-child(8n+3) { border-top: 4px solid #fbbf24; }
.grade-tile:nth-child(8n+4) { border-top: 4px solid #34d399; }
.grade-tile:nth-child(8n+5) { border-top: 4px solid #4cc9f0; }
.grade-tile:nth-child(8n+6) { border-top: 4px solid #60a5fa; }
.grade-tile:nth-child(8n+7) { border-top: 4px solid #a78bfa; }
.grade-tile:nth-child(8n+0) { border-top: 4px solid #e879f9; }

.grade-tile:nth-child(8n+1):hover { box-shadow: 0 0 0 1px #f472b6, 0 16px 40px -12px rgba(244,114,182,.5); }
.grade-tile:nth-child(8n+2):hover { box-shadow: 0 0 0 1px #fb923c, 0 16px 40px -12px rgba(251,146,60,.5); }
.grade-tile:nth-child(8n+3):hover { box-shadow: 0 0 0 1px #fbbf24, 0 16px 40px -12px rgba(251,191,36,.5); }
.grade-tile:nth-child(8n+4):hover { box-shadow: 0 0 0 1px #34d399, 0 16px 40px -12px rgba(52,211,153,.5); }
.grade-tile:nth-child(8n+5):hover { box-shadow: 0 0 0 1px #4cc9f0, 0 16px 40px -12px rgba(76,201,240,.5); }
.grade-tile:nth-child(8n+6):hover { box-shadow: 0 0 0 1px #60a5fa, 0 16px 40px -12px rgba(96,165,250,.5); }
.grade-tile:nth-child(8n+7):hover { box-shadow: 0 0 0 1px #a78bfa, 0 16px 40px -12px rgba(167,139,250,.5); }
.grade-tile:nth-child(8n+0):hover { box-shadow: 0 0 0 1px #e879f9, 0 16px 40px -12px rgba(232,121,249,.5); }

.grade-tile:hover { transform: translateY(-5px) scale(1.03); }

.grade-num {
  font-size: 42px; font-weight: 900; line-height: 1;
  background: linear-gradient(135deg, var(--accent), var(--violet));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.grade-icon { font-size: 28px; }
.grade-label { font-size: 15px; font-weight: 800; margin-top: 2px; }
.grade-sub { font-size: 11px; color: var(--muted); font-weight: 500; }

/* ===== APP NAV ===== */
.app-nav {
  display: flex; gap: 6px; flex-wrap: wrap;
  padding: 10px clamp(16px,4vw,40px);
  background: rgba(255,255,255,0.03);
  border-bottom: 1px solid rgba(255,255,255,0.06);
  position: relative; z-index: 1;
}
.nav-btn {
  background: rgba(255,255,255,0.05); color: var(--muted);
  border: 1px solid rgba(255,255,255,0.08);
  padding: 7px 16px; border-radius: 999px; cursor: pointer;
  font: inherit; font-size: 13px; font-weight: 700;
  transition: all .18s ease;
}
.nav-btn:hover { background: rgba(255,255,255,0.10); color: var(--text); transform: translateY(-1px); }
.nav-btn.active { background: linear-gradient(135deg,rgba(167,139,250,0.25),rgba(244,114,182,0.15)); border-color: rgba(167,139,250,0.4); color: var(--text); }

/* ===== PANEL CARD ===== */
.panel-card {
  background: linear-gradient(160deg, var(--card), var(--card-2));
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: 20px; padding: clamp(20px,4vw,32px);
  box-shadow: var(--shadow); margin-bottom: 20px;
}
.panel-desc { color: var(--muted); font-size: 14px; margin: 0 0 18px; line-height: 1.6; }

/* ===== LEADERBOARD ===== */
.lb-list { display: flex; flex-direction: column; gap: 10px; }
.lb-row {
  display: flex; align-items: center; gap: 14px;
  background: linear-gradient(160deg, var(--card), var(--card-2));
  border: 1px solid rgba(255,255,255,0.07);
  border-radius: 14px; padding: 14px 18px;
  transition: transform .15s ease, box-shadow .15s ease;
}
.lb-row:hover { transform: translateY(-2px); box-shadow: 0 8px 24px -8px rgba(0,0,0,0.5); }
.lb-row.lb-me { border-color: rgba(167,139,250,0.4); background: linear-gradient(160deg,rgba(167,139,250,0.08),rgba(244,114,182,0.05)); }
.lb-rank { min-width: 38px; text-align: center; font-size: 22px; font-weight: 900; }
.lb-rank.gold   { color: #fbbf24; text-shadow: 0 0 12px rgba(251,191,36,0.7); }
.lb-rank.silver { color: #94a3b8; text-shadow: 0 0 10px rgba(148,163,184,0.5); }
.lb-rank.bronze { color: #fb923c; text-shadow: 0 0 10px rgba(251,146,60,0.5); }
.lb-name { flex: 1; font-weight: 700; font-size: 15px; }
.lb-trophy { font-size: 18px; }
.lb-xp { font-size: 18px; font-weight: 900; color: var(--primary); text-shadow: 0 0 8px rgba(255,176,32,0.5); min-width: 70px; text-align: right; }
.lb-you { font-size: 10px; color: var(--violet); font-weight: 700; letter-spacing: 0.05em; background: rgba(167,139,250,0.15); padding: 2px 8px; border-radius: 999px; }

/* ===== STATS ===== */
.stats-overview {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(130px,1fr)); gap: 12px; margin-bottom: 24px;
}
.stats-card {
  background: linear-gradient(160deg, var(--card), var(--card-2));
  border: 1px solid rgba(255,255,255,0.07);
  border-radius: 16px; padding: 16px 18px; text-align: center;
}
.stats-card .sc-val { font-size: 32px; font-weight: 900; margin-bottom: 4px; }
.stats-card .sc-label { font-size: 11px; color: var(--muted); font-weight: 700; text-transform: uppercase; letter-spacing: 0.07em; }
.stats-card.xp-card .sc-val  { color: var(--primary); text-shadow: 0 0 12px rgba(255,176,32,0.5); }
.stats-card.ok-card .sc-val  { color: var(--green);   text-shadow: 0 0 12px rgba(52,211,153,0.5); }
.stats-card.err-card .sc-val { color: var(--red);     text-shadow: 0 0 12px rgba(248,113,113,0.4); }
.stats-card.pct-card .sc-val { color: var(--accent);  text-shadow: 0 0 12px rgba(76,201,240,0.5); }
.stats-table { display: flex; flex-direction: column; gap: 6px; }
.stats-row {
  display: flex; justify-content: space-between; align-items: center;
  background: rgba(255,255,255,0.04); border: 1px solid rgba(255,255,255,0.06);
  border-radius: 10px; padding: 10px 14px; font-size: 14px;
}
.stats-row .sr-topic { color: var(--text); font-weight: 600; }
.stats-row .sr-grade { font-size: 11px; color: var(--muted); margin-top: 2px; }
.stats-row .sr-nums  { font-weight: 800; }
.stats-row .sr-pct   { font-size: 12px; color: var(--muted); }
.stats-section-h { font-size: 15px; color: var(--violet); font-weight: 700; margin: 20px 0 10px; }
.stats-empty { color: var(--muted); font-size: 14px; padding: 20px 0; text-align: center; }

/* ===== JOIN CLASS ===== */
.join-row { display: flex; gap: 10px; align-items: center; flex-wrap: wrap; }
.code-input {
  flex: 1; min-width: 160px; max-width: 220px;
  padding: 13px 16px; font-size: 22px; font-weight: 900; letter-spacing: 0.15em;
  background: rgba(0,0,0,0.3); color: var(--text);
  border: 2px solid rgba(255,255,255,0.10); border-radius: 12px;
  outline: none; text-transform: uppercase; transition: border-color .2s;
}
.code-input:focus { border-color: var(--violet); box-shadow: 0 0 0 4px rgba(167,139,250,0.2); }
.join-msg { font-size: 14px; margin-top: 14px; font-weight: 700; padding: 10px 14px; border-radius: 10px; }
.join-msg.hidden { display: none; }
.join-msg.ok  { background: rgba(52,211,153,0.1);  color: var(--green); border: 1px solid rgba(52,211,153,0.25); }
.join-msg.err { background: rgba(248,113,113,0.1); color: var(--red);   border: 1px solid rgba(248,113,113,0.25); }

/* ===== TEACHER ===== */
.class-code-box {
  text-align: center; padding: 28px; margin-bottom: 20px;
  background: linear-gradient(135deg, rgba(167,139,250,0.1), rgba(244,114,182,0.06));
  border: 1px solid rgba(167,139,250,0.3); border-radius: 18px;
}
.class-code-box .code-label { font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: 0.1em; margin-bottom: 10px; font-weight: 700; }
.class-code-box .code-val {
  font-size: 48px; font-weight: 900; letter-spacing: 0.2em;
  background: linear-gradient(90deg, var(--accent), var(--violet), var(--pink));
  -webkit-background-clip: text; background-clip: text; color: transparent;
  animation: rainbowFlow 3s linear infinite; cursor: pointer;
}
.class-code-box .code-hint { font-size: 12px; color: var(--muted); margin-top: 8px; }
.students-list { display: flex; flex-direction: column; gap: 8px; }
.student-row {
  display: flex; align-items: center; gap: 14px;
  background: rgba(255,255,255,0.04); border: 1px solid rgba(255,255,255,0.07);
  border-radius: 12px; padding: 12px 16px; cursor: pointer;
  transition: all .15s ease;
}
.student-row:hover { background: rgba(255,255,255,0.08); transform: translateX(3px); }
.student-name { flex: 1; font-weight: 700; font-size: 15px; }
.student-xp { font-weight: 900; color: var(--primary); font-size: 14px; }
.student-arrow { color: var(--muted); font-size: 16px; }
.no-students { color: var(--muted); text-align: center; padding: 30px 0; font-size: 14px; }
.create-class-form { display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 16px; }
.class-name-input {
  flex: 1; min-width: 180px; padding: 12px 14px;
  background: rgba(0,0,0,0.3); color: var(--text);
  border: 2px solid rgba(255,255,255,0.10); border-radius: 12px;
  font: inherit; font-size: 15px; outline: none; transition: border-color .2s;
}
.class-name-input:focus { border-color: var(--violet); box-shadow: 0 0 0 3px rgba(167,139,250,0.2); }

/* ===== TEACHER WELCOME ===== */
.teacher-welcome {
  background: linear-gradient(160deg, rgba(167,139,250,0.10), rgba(244,114,182,0.06));
  border: 1px solid rgba(167,139,250,0.25);
  border-radius: 20px; padding: clamp(20px,4vw,32px);
  margin-bottom: 20px;
}
.tw-title { font-size: 20px; font-weight: 900; margin-bottom: 10px; }
.tw-desc  { color: var(--muted); font-size: 14px; margin: 0 0 22px; line-height: 1.6; }
.tw-steps { display: flex; flex-direction: column; gap: 14px; }
.tw-step  { display: flex; align-items: flex-start; gap: 16px; }
.tw-step-num {
  min-width: 32px; height: 32px; border-radius: 50%;
  background: linear-gradient(135deg, var(--violet), var(--pink));
  display: flex; align-items: center; justify-content: center;
  font-size: 14px; font-weight: 900; color: #fff; flex-shrink: 0;
  box-shadow: 0 4px 12px -4px rgba(167,139,250,0.6);
}
.tw-step-title { font-weight: 800; font-size: 15px; margin-bottom: 3px; }
.tw-step-desc  { color: var(--muted); font-size: 13px; line-height: 1.5; }

/* ===== FOOTER ===== */
.foot {
  text-align: center; color: var(--muted); padding: 24px 16px 32px; font-size: 12px;
}

/* ===== RESPONSIVE ===== */
@media (max-width: 520px) {
  .stats { gap: 6px; }
  .stat { padding: 6px 10px; min-width: 60px; }
  .stat span:last-child { font-size: 16px; }
  .brand h1 { font-size: 18px; }
  .brand .tag { font-size: 12px; }
}