/* ============================================================
   COMPONENTS.CSS — Canonical UI component library (v4.1.0)
   ------------------------------------------------------------
   All styling is driven by design tokens (tokens.css) so every
   component works in both the dark (default) and light themes.
   This file is loaded after screens.css and is therefore the
   authoritative source for shared component classes.
   ============================================================ */

/* ============================================================
   PRIMITIVES — generic reusable classes for new UI
   ============================================================ */

/* Base button reset for all interactive controls */
.btn,
.back-btn,
.pause-btn,
.back-to-mode-btn,
.submit-btn,
.start-btn,
.start-pvp-btn,
.start-challenge-btn,
.skip-challenge-btn,
.result-btn,
.explanation-btn,
.difficulty-btn,
.add-player-btn,
.add-pvp-player-btn,
.remove-player-btn,
.remove-pvp-player-btn,
.ranking-save-btn,
.ranking-tab {
  font-family: var(--font-body);
  border: none;
  cursor: pointer;
  -webkit-appearance: none;
  appearance: none;
  transition: transform var(--dur-fast) var(--ease-out),
              background-color var(--dur-fast) var(--ease-out),
              border-color var(--dur-fast) var(--ease-out),
              box-shadow var(--dur-fast) var(--ease-out),
              color var(--dur-fast) var(--ease-out);
}

/* Generic button (new) */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  min-height: 48px;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-md);
  font-weight: 800;
  font-size: 1rem;
  line-height: 1;
  background: var(--surface-2);
  color: var(--text);
  border: 1.5px solid var(--border);
}
.btn:hover { background: var(--surface-hover); transform: translateY(-1px); }
.btn:active { transform: scale(0.98); }
.btn--primary { background: var(--primary); color: var(--text-on-accent); border-color: transparent; box-shadow: var(--shadow-md); }
.btn--primary:hover { background: var(--primary-hover); }
.btn--success { background: var(--success); color: var(--text-on-accent); border-color: transparent; }
.btn--danger  { background: var(--error);   color: var(--text-on-accent); border-color: transparent; }
.btn--ghost   { background: transparent; border-color: var(--border-strong); }
.btn--lg { min-height: 56px; padding: 1rem 2rem; font-size: 1.125rem; }
.btn--block { width: 100%; }

/* Generic surface card (new) */
.card {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
  padding: var(--space-5);
}

/* Generic badge / pill (new) */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-pill);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.02em;
  background: var(--surface-2);
  color: var(--text-muted);
  border: 1px solid var(--border);
}
.badge--success { background: color-mix(in srgb, var(--success) 16%, transparent); color: var(--success); border-color: color-mix(in srgb, var(--success) 40%, transparent); }
.badge--error   { background: color-mix(in srgb, var(--error) 16%, transparent);   color: var(--error);   border-color: color-mix(in srgb, var(--error) 40%, transparent); }
.badge--warn    { background: color-mix(in srgb, var(--warn) 16%, transparent);    color: var(--warn);    border-color: color-mix(in srgb, var(--warn) 40%, transparent); }
.badge--primary { background: color-mix(in srgb, var(--primary) 16%, transparent); color: var(--primary); border-color: color-mix(in srgb, var(--primary) 40%, transparent); }

/* Avatar (new) */
.avatar {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: var(--radius-pill);
  background: var(--surface-2);
  border: 1.5px solid var(--border);
  font-size: 1.375rem;
  line-height: 1;
  flex-shrink: 0;
}
.avatar--sm { width: 34px; height: 34px; font-size: 1.0625rem; }
.avatar--lg { width: 64px; height: 64px; font-size: 2rem; }

/* Progress bar (new) */
.progress {
  height: 10px;
  border-radius: var(--radius-pill);
  background: var(--surface-2);
  overflow: hidden;
}
.progress__bar {
  height: 100%;
  width: 0;
  border-radius: inherit;
  background: linear-gradient(90deg, var(--primary), var(--info));
  transition: width var(--dur-base) var(--ease-out);
}

/* ============================================================
   NAVIGATION BUTTONS
   ============================================================ */
.back-btn,
.back-to-mode-btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  min-height: 44px;
  background: var(--surface-2);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-pill);
  padding: 0.5rem 1.125rem;
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--text-muted);
}
.back-btn:hover,
.back-to-mode-btn:hover {
  background: var(--surface-hover);
  color: var(--text);
  transform: translateX(-2px);
}

.pause-btn {
  background: color-mix(in srgb, var(--accent-violet) 18%, transparent);
  border: 1.5px solid color-mix(in srgb, var(--accent-violet) 40%, transparent);
  border-radius: var(--radius-pill);
  min-height: 44px;
  padding: 0.5rem 1rem;
  font-size: 0.8125rem;
  font-weight: 800;
  letter-spacing: 0.02em;
  color: var(--accent-violet);
}
.pause-btn:hover { background: color-mix(in srgb, var(--accent-violet) 32%, transparent); color: var(--text); }
.pause-btn.paused { background: color-mix(in srgb, var(--primary) 18%, transparent); border-color: color-mix(in srgb, var(--primary) 40%, transparent); color: var(--primary); }
.pause-btn.paused:hover { background: color-mix(in srgb, var(--primary) 32%, transparent); color: var(--text); }

/* ============================================================
   PRIMARY ACTION BUTTONS
   ============================================================ */
.submit-btn,
.explanation-btn {
  background: var(--primary);
  border: none;
  border-radius: var(--radius-md);
  min-height: 48px;
  padding: 0.875rem 1.625rem;
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text-on-accent);
  box-shadow: var(--shadow-md);
}
.submit-btn:hover,
.explanation-btn:hover { background: var(--primary-hover); transform: translateY(-2px); box-shadow: var(--shadow-lg); }
.submit-btn:active,
.explanation-btn:active { transform: scale(0.97); }
.submit-btn:disabled { opacity: 0.45; pointer-events: none; box-shadow: none; }

.start-pvp-btn {
  background: linear-gradient(135deg, var(--primary), var(--accent-violet));
  border: none;
  border-radius: var(--radius-pill);
  min-height: 56px;
  padding: 1rem 2.5rem;
  font-family: var(--font-display);
  font-size: 1.375rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text-on-accent);
  box-shadow: var(--shadow-md);
  margin-bottom: 0.75rem;
}
.start-pvp-btn:hover { transform: translateY(-3px); box-shadow: var(--shadow-lg); }

.start-btn {
  width: 100%;
  min-height: 56px;
  padding: 1rem 2rem;
  background: linear-gradient(135deg, var(--success), var(--info));
  border: none;
  border-radius: var(--radius-md);
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text-on-accent);
  box-shadow: var(--shadow-md);
}
.start-btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); filter: brightness(1.05); }

.start-challenge-btn {
  background: linear-gradient(135deg, var(--accent-violet), var(--accent-pink));
  border: none;
  border-radius: var(--radius-pill);
  min-height: 56px;
  padding: 1rem 2rem;
  font-family: var(--font-display);
  font-size: 1.375rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text-on-accent);
  box-shadow: var(--shadow-md);
  display: block;
  width: 100%;
  margin-bottom: 0.75rem;
}
.start-challenge-btn:hover { transform: translateY(-3px); box-shadow: var(--shadow-lg); }

.skip-challenge-btn {
  background: transparent;
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius-pill);
  min-height: 44px;
  padding: 0.625rem 1.875rem;
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--text-muted);
  display: block;
  width: 100%;
}
.skip-challenge-btn:hover { color: var(--text); border-color: var(--border-strong); background: var(--surface-2); }

/* Result action buttons */
.result-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  width: 100%;
  min-height: 52px;
  border: none;
  border-radius: var(--radius-md);
  padding: 1rem;
  font-family: var(--font-display);
  font-size: 1.25rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text-on-accent);
  background: var(--primary);
  box-shadow: var(--shadow-md);
  margin-bottom: 0.625rem;
}
.result-btn:hover { transform: translateY(-2px); box-shadow: var(--shadow-lg); background: var(--primary-hover); }
.result-btn.primary { background: linear-gradient(135deg, var(--primary), var(--accent-violet)); }
.result-btn.secondary,
.result-btn.home-btn {
  background: var(--surface-2);
  border: 1.5px solid var(--border);
  color: var(--text);
  box-shadow: none;
}
.result-btn.secondary:hover,
.result-btn.home-btn:hover { background: var(--surface-hover); border-color: var(--border-strong); }

/* ============================================================
   CHOICE / ANSWER BUTTONS
   ============================================================ */
.answer-btn {
  background: var(--surface);
  border: 2px solid var(--border);
  border-radius: var(--radius-md);
  padding: clamp(0.875rem, 0.6rem + 0.9vw, 1.75rem) clamp(0.875rem, 0.7rem + 0.6vw, 1.5rem);
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 1.05rem + 1.3vw, 2.75rem);
  font-weight: 700;
  letter-spacing: 0.03em;
  color: var(--text);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: clamp(3.5rem, 3rem + 1.6vw, 5.5rem);
  line-height: 1.3;
  transition: transform var(--dur-fast) var(--ease-out),
              border-color var(--dur-fast) var(--ease-out),
              background-color var(--dur-fast) var(--ease-out),
              box-shadow var(--dur-fast) var(--ease-out);
}
.answer-btn:hover {
  border-color: var(--primary);
  background: color-mix(in srgb, var(--primary) 8%, var(--surface));
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
}
.answer-btn:active { transform: scale(0.97); }
.answer-btn:disabled { pointer-events: none; }
.answer-btn.correct-ans {
  background: color-mix(in srgb, var(--success) 18%, transparent);
  border-color: var(--success);
  color: var(--success);
}
.answer-btn.wrong-ans {
  background: color-mix(in srgb, var(--error) 18%, transparent);
  border-color: var(--error);
  color: var(--error);
}
.answer-btn .katex { font-size: 1em; letter-spacing: normal; }
.answer-btn .katex .frac-line { border-top-width: 2px; }

.difficulty-btn {
  min-height: 44px;
  padding: 0.625rem 1.25rem;
  background: var(--surface-2);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--text);
}
.difficulty-btn:hover { border-color: var(--primary); }
.difficulty-btn.selected {
  background: color-mix(in srgb, var(--success) 20%, transparent);
  border-color: var(--success);
  color: var(--success);
}

.add-player-btn,
.add-pvp-player-btn {
  width: 100%;
  min-height: 44px;
  padding: 0.625rem;
  background: color-mix(in srgb, var(--success) 12%, transparent);
  border: 1.5px dashed color-mix(in srgb, var(--success) 40%, transparent);
  border-radius: var(--radius-sm);
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--success);
}
.add-player-btn:hover,
.add-pvp-player-btn:hover { background: color-mix(in srgb, var(--success) 22%, transparent); }

.remove-player-btn,
.remove-pvp-player-btn {
  min-width: 2.75rem;
  min-height: 2.75rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--error) 14%, transparent);
  border: 1px solid color-mix(in srgb, var(--error) 32%, transparent);
  border-radius: var(--radius-sm);
  color: var(--error);
  font-size: 0.875rem;
  font-weight: 800;
  flex-shrink: 0;
}
.remove-player-btn:hover,
.remove-pvp-player-btn:hover { background: color-mix(in srgb, var(--error) 28%, transparent); }

/* ============================================================
   PILLS, BADGES & STATS
   ============================================================ */
.stat-pill {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-pill);
  padding: 0.5rem 1rem;
  display: flex;
  align-items: center;
  gap: 0.375rem;
  font-weight: 800;
  font-size: 0.9375rem;
  color: var(--text);
}
.score-pill  { border-color: color-mix(in srgb, var(--success) 40%, transparent); color: var(--success); }
.lives-pill  { border-color: color-mix(in srgb, var(--error) 40%, transparent);   color: var(--error); }
.streak-pill { border-color: color-mix(in srgb, var(--warn) 40%, transparent);    color: var(--warn); }

.eq-type-badge {
  display: inline-block;
  background: color-mix(in srgb, var(--primary) 14%, transparent);
  color: var(--primary);
  border: 1px solid color-mix(in srgb, var(--primary) 32%, transparent);
  border-radius: var(--radius-pill);
  padding: 0.25rem 0.875rem;
  font-size: 0.6875rem;
  font-weight: 800;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  margin-bottom: 0.875rem;
}

.new-hs-badge {
  background: linear-gradient(135deg, var(--accent-yellow), var(--accent-orange));
  color: #1a1200;
  border-radius: var(--radius-pill);
  padding: 0.375rem 1.25rem;
  font-weight: 900;
  font-size: 0.875rem;
  letter-spacing: 0.04em;
  display: inline-block;
  margin-bottom: 1rem;
}

/* Segmented tabs (ranking, filters) */
.ranking-tab {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  min-height: 44px;
  padding: 0.625rem 0.875rem;
  background: var(--surface-2);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--text-muted);
  white-space: nowrap;
}
.ranking-tab:hover { background: var(--surface-hover); color: var(--text); }
.ranking-tab.active {
  background: color-mix(in srgb, var(--primary) 16%, transparent);
  border-color: var(--primary);
  color: var(--text);
  box-shadow: 0 0 0 1px color-mix(in srgb, var(--primary) 35%, transparent);
}

/* ============================================================
   FORM INPUTS
   ============================================================ */
.eq-input,
.team-input,
.player-input,
.pvp-player-input,
.ranking-name-input,
.player-input-group input {
  font-family: var(--font-body);
  background: var(--surface-2);
  border: 1.5px solid var(--border-strong);
  border-radius: var(--radius-md);
  color: var(--text);
  transition: border-color var(--dur-fast) var(--ease-out),
              box-shadow var(--dur-fast) var(--ease-out),
              background-color var(--dur-fast) var(--ease-out);
}
.eq-input::placeholder,
.team-input::placeholder,
.player-input::placeholder,
.pvp-player-input::placeholder,
.ranking-name-input::placeholder,
.player-input-group input::placeholder { color: var(--text-faint); }

.eq-input:focus,
.team-input:focus,
.player-input:focus,
.pvp-player-input:focus,
.ranking-name-input:focus,
.player-input-group input:focus {
  outline: none;
  border-color: var(--primary);
  background: var(--surface);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--primary) 28%, transparent);
}

.eq-input {
  flex: 1;
  padding: clamp(0.75rem, 0.6rem + 0.6vw, 1.25rem) clamp(1rem, 0.8rem + 0.8vw, 1.5rem);
  font-family: var(--font-display);
  font-size: clamp(1.75rem, 1.2rem + 1.5vw, 3rem);
  letter-spacing: 0.04em;
  text-align: center;
}
.eq-input.correct-ans { border-color: var(--success); color: var(--success); }
.eq-input.wrong-ans   { border-color: var(--error);   color: var(--error); }

.player-input-group {
  display: flex;
  flex-direction: column;
}
.player-input-group label {
  font-size: 0.875rem;
  font-weight: 700;
  color: var(--success);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: 0.5rem;
}
.player-input-group input {
  padding: 0.875rem 1rem;
  font-size: 1rem;
}

.pvp-player-input { flex: 1; padding: 0.625rem 0.75rem; font-size: 0.9375rem; border-radius: var(--radius-md); }
.team-input { width: 100%; padding: 0.625rem 0.75rem; font-size: 0.875rem; margin-bottom: 0.75rem; border-radius: var(--radius-sm); }
.player-input { flex: 1; padding: 0.625rem 0.75rem; font-size: 0.875rem; border-radius: var(--radius-sm); }
.ranking-name-input { flex: 1; padding: 0.625rem 0.875rem; font-size: 0.9375rem; border-radius: var(--radius-sm); }

/* ============================================================
   SURFACES / CARDS (shared across screens)
   ============================================================ */
.final-player-card,
.final-side-card,
.stat-box,
.team-form,
.container-form {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-md);
}

.final-player-card { padding: 1.875rem 1.25rem; text-align: center; border-color: color-mix(in srgb, var(--primary) 25%, transparent); }
.final-player-name { font-family: var(--font-display); font-size: 1.125rem; font-weight: 700; color: var(--text-muted); letter-spacing: 0.02em; margin-bottom: 0.75rem; }
.final-player-score { font-family: var(--font-display); font-size: 3rem; font-weight: 800; color: var(--text); margin-bottom: 0.75rem; }
.final-player-status { font-size: 0.8125rem; font-weight: 700; letter-spacing: 0.02em; }

.final-side-card { padding: 1.25rem 1rem; text-align: center; }
.final-side-card.winning-side { border-color: var(--success); box-shadow: 0 0 0 1px color-mix(in srgb, var(--success) 40%, transparent), var(--shadow-md); }
.final-side-card.losing-side  { border-color: var(--border); opacity: 0.85; }
.final-side-label { font-family: var(--font-display); font-size: 1.125rem; font-weight: 700; letter-spacing: 0.02em; color: var(--text); margin-bottom: 0.25rem; }
.final-side-total { font-family: var(--font-display); font-size: 1.875rem; font-weight: 800; color: var(--text); margin-bottom: 0.75rem; }

.stat-box { padding: 1.25rem; text-align: center; }
.stat-label { font-size: 0.6875rem; font-weight: 800; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; margin-bottom: 0.75rem; }
.stat-value { font-family: var(--font-display); font-size: 1.75rem; font-weight: 800; color: var(--text); letter-spacing: 0.02em; }
.stat-row { display: flex; justify-content: space-around; font-family: var(--font-display); font-size: 1.375rem; font-weight: 700; color: var(--text); }

.team-form { padding: 1.25rem; border-radius: var(--radius-md); }
.container-form { padding: 1.875rem; max-width: min(56.25rem, 90vw); margin: 0 auto; border-radius: var(--radius-lg); }

.winner {
  color: var(--success);
  text-transform: uppercase;
  background: color-mix(in srgb, var(--success) 15%, transparent);
  padding: 0.375rem 0.75rem;
  border-radius: var(--radius-sm);
  display: inline-block;
}
.loser { color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.02em; }
.tie {
  color: var(--primary);
  text-transform: uppercase;
  background: color-mix(in srgb, var(--primary) 15%, transparent);
  padding: 0.375rem 0.75rem;
  border-radius: var(--radius-sm);
  display: inline-block;
}

/* ============================================================
   PvP / COMPETITION STRUCTURE
   ============================================================ */
.pvp-header { text-align: center; margin-bottom: 2.5rem; }
.pvp-icon { font-size: 5rem; display: block; margin-bottom: 1rem; }
.pvp-header h2 {
  font-family: var(--font-display);
  font-size: 2.5rem;
  font-weight: 800;
  color: var(--accent-pink);
  letter-spacing: 0.02em;
  margin: 0;
}
.pvp-subtitle { font-size: 0.8125rem; color: var(--text-muted); margin: 0.25rem 0 0; letter-spacing: 0.02em; }

.players-form { display: flex; flex-direction: column; gap: 1.25rem; margin: 0 auto 2.5rem; max-width: 18.75rem; }
.vs-divider { text-align: center; font-size: 1.5rem; font-weight: 900; color: var(--primary); margin: 0.625rem 0; }

/* PvP team-name entry (multi player) */
.pvp-teams-form {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  gap: 1rem;
  align-items: start;
  width: 100%;
  max-width: 35rem;
  margin: 0 auto 1.75rem;
}
.pvp-team-form { display: flex; flex-direction: column; gap: 0.625rem; }
.pvp-side-title { font-family: var(--font-display); font-size: 1.25rem; font-weight: 700; letter-spacing: 0.02em; margin: 0 0 0.375rem; color: var(--text); }
.pvp-players-list { display: flex; flex-direction: column; gap: 0.5rem; }
.pvp-player-row { display: flex; gap: 0.375rem; align-items: center; }
.pvp-vs-sep { font-family: var(--font-display); font-size: 1.75rem; font-weight: 800; color: var(--accent-pink); letter-spacing: 0.02em; padding-top: 2rem; text-align: center; }

/* PvP round bar / matchup */
.pvp-round-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--surface-2);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  padding: 0.625rem 1.25rem;
  gap: 1rem;
}
.pvp-round-tag { font-family: var(--font-display); font-size: 1.125rem; font-weight: 700; letter-spacing: 0.04em; color: var(--text-muted); white-space: nowrap; }
.pvp-matchup-bar { display: flex; align-items: center; gap: 0.875rem; flex: 1; justify-content: center; }
.pvp-match-name { font-family: var(--font-display); font-size: 1.375rem; font-weight: 700; letter-spacing: 0.02em; max-width: 12.5rem; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.p1-match { color: var(--primary); }
.p2-match { color: var(--accent-pink); }
.pvp-match-vs { font-size: 1.125rem; color: var(--text-faint); }
.pvp-answered-msg {
  background: color-mix(in srgb, var(--success) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--success) 32%, transparent);
  border-radius: var(--radius-md);
  padding: 0.625rem 1rem;
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--success);
  text-align: center;
  margin-top: 0.5rem;
  animation: fade-in var(--dur-base) var(--ease-out);
}
.pvp-active-turn { opacity: 1; transition: opacity var(--dur-fast) var(--ease-out); }
.pvp-inactive-turn { opacity: 0.4; pointer-events: none; transition: opacity var(--dur-fast) var(--ease-out); }
.pvp-match-active { font-size: 1.625rem; color: var(--text); }

/* PvP game top bar */
.pvp-top-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 1rem 1.25rem;
  gap: 0.75rem;
  background: var(--surface-2);
  border-bottom: 1px solid var(--border);
  margin-bottom: 0.75rem;
}
.pvp-scores { display: flex; align-items: center; gap: 1.25rem; flex: 1; justify-content: center; }
.pvp-scores .player-score {
  text-align: center;
  padding: 0.625rem 1.25rem;
  border-radius: var(--radius-md);
  min-width: 6.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
}
.pvp-scores .player1-score { border-color: color-mix(in srgb, var(--primary) 40%, transparent); background: color-mix(in srgb, var(--primary) 8%, transparent); }
.pvp-scores .player2-score { border-color: color-mix(in srgb, var(--accent-pink) 40%, transparent); background: color-mix(in srgb, var(--accent-pink) 8%, transparent); }
.pvp-scores .player-name { font-size: 0.75rem; font-weight: 700; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.04em; margin-bottom: 0.25rem; }
.player-points { font-family: var(--font-display); font-size: 2rem; font-weight: 800; color: var(--text); letter-spacing: 0.02em; }

/* Neutral player name/score (team results, rankings) — theme-aware */
.player-name { font-weight: 600; color: var(--text); }
.player-score { font-weight: 700; color: var(--primary); }
.vs-text { font-family: var(--font-display); font-size: 1.25rem; font-weight: 800; color: var(--accent-pink); letter-spacing: 0.04em; }

.current-player-banner {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  background: color-mix(in srgb, var(--primary) 12%, transparent);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 0.75rem 1.25rem;
  margin-bottom: 0.75rem;
  animation: pulse 2s ease-in-out infinite;
}
#current-player-icon { font-size: 1.5rem; }
#current-player-name { font-family: var(--font-display); font-size: 1.125rem; font-weight: 700; color: var(--primary); letter-spacing: 0.02em; text-transform: uppercase; }

@keyframes pulse {
  0%, 100% { background: color-mix(in srgb, var(--primary) 10%, transparent); }
  50%      { background: color-mix(in srgb, var(--primary) 20%, transparent); }
}

/* PvP result */
.result-header { text-align: center; margin-bottom: 2.5rem; }
#result-icon { font-size: 6.25rem; display: block; margin-bottom: 1.25rem; animation: bounce 0.6s ease-in-out; }
#result-title {
  font-family: var(--font-display);
  font-size: 3rem;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), var(--accent-pink));
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: 0.02em;
}
.pvp-final-scores { display: grid; grid-template-columns: 1fr auto 1fr; gap: 1.25rem; max-width: 31.25rem; margin: 0 auto 2.5rem; align-items: center; }
.vs-separator { font-size: 2rem; font-weight: 900; color: var(--accent-pink); letter-spacing: 0.02em; }
.pvp-stats { display: grid; grid-template-columns: 1fr; gap: 1rem; max-width: 31.25rem; margin: 0 auto 2.5rem; }
.result-buttons { display: flex; flex-direction: column; gap: 0.75rem; max-width: 18.75rem; margin: 0 auto; }

.pvp-player-result-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem;
  font-size: 0.8125rem;
  padding: 0.3125rem 0.5rem;
  border-radius: var(--radius-sm);
  background: var(--surface-2);
  margin-bottom: 0.3125rem;
}
.pvp-player-result-name { font-weight: 700; color: var(--text); flex: 1; text-align: left; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.pvp-player-result-score { font-family: var(--font-display); font-size: 1rem; font-weight: 700; color: var(--success); letter-spacing: 0.02em; }
.pvp-player-result-correct { font-size: 0.75rem; font-weight: 700; color: var(--text-faint); }

/* ============================================================
   CHALLENGE BANNER
   ============================================================ */
.challenge-banner {
  background: color-mix(in srgb, var(--accent-violet) 14%, transparent);
  border: 1.5px solid color-mix(in srgb, var(--accent-violet) 45%, transparent);
  border-radius: var(--radius-md);
  padding: 0.75rem 1.125rem;
  margin-bottom: 0.875rem;
  display: none;
  align-items: center;
  gap: 0.75rem;
  animation: slide-in var(--dur-base) var(--ease-bounce);
}
.challenge-banner.visible { display: flex; }
.challenge-icon { font-size: 1.875rem; }
.challenge-title { font-family: var(--font-display); font-size: 1.125rem; font-weight: 700; letter-spacing: 0.02em; color: var(--accent-violet); }
.challenge-desc { font-size: 0.75rem; font-weight: 600; color: var(--text-muted); }

/* ============================================================
   TOAST
   ============================================================ */
.feedback-toast {
  position: fixed;
  top: 12%;
  left: 50%;
  transform: translate(-50%, -12px) scale(0.9);
  opacity: 0;
  background: var(--surface);
  border: 2px solid var(--success);
  border-radius: var(--radius-lg);
  padding: 1rem 2rem;
  font-family: var(--font-display);
  font-size: clamp(1.375rem, 5vw, 2.25rem);
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--success);
  z-index: 9999;
  transition: all var(--dur-base) var(--ease-bounce);
  max-width: min(90vw, 40rem);
  white-space: normal;
  text-align: center;
  box-shadow: var(--shadow-xl);
  pointer-events: none;
}
.feedback-toast.wrong-toast { border-color: var(--error); color: var(--error); }
.feedback-toast.show { transform: translate(-50%, 0) scale(1); opacity: 1; }

/* ============================================================
   EXPLANATION MODAL
   ============================================================ */
.explanation-modal {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  background: rgba(10, 12, 18, 0.66);
  backdrop-filter: blur(6px);
  -webkit-backdrop-filter: blur(6px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1rem;
  z-index: 1000;
  opacity: 0;
  pointer-events: none;
  transition: opacity var(--dur-base) var(--ease-out);
}
.explanation-modal.show { opacity: 1; pointer-events: auto; }
.explanation-content {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-lg);
  padding: clamp(1.5rem, 1rem + 2vw, 2.75rem);
  width: 92%;
  max-width: min(38rem, 92vw);
  text-align: center;
  transform: translateY(20px);
  transition: transform var(--dur-slow) var(--ease-bounce);
  box-shadow: var(--shadow-xl);
}
.explanation-modal.show .explanation-content { transform: translateY(0); }
.explanation-title {
  font-family: var(--font-display);
  font-size: clamp(1.875rem, 1.2rem + 1.6vw, 2.75rem);
  font-weight: 800;
  color: var(--primary);
  letter-spacing: 0.02em;
  margin: 0 0 1.625rem;
}
.explanation-steps {
  text-align: left;
  font-size: clamp(1.05rem, 0.95rem + 0.5vw, 1.4rem);
  color: var(--text);
  margin-bottom: 2rem;
  display: flex;
  flex-direction: column;
  gap: var(--space-4);
  max-height: 62vh;
  overflow-y: auto;
  padding-right: 0.375rem;
}
.explanation-steps::-webkit-scrollbar { width: 6px; }
.explanation-steps::-webkit-scrollbar-thumb { background: var(--border-strong); border-radius: 10px; }
.explanation-step {
  background: var(--surface-2);
  padding: clamp(1rem, 0.8rem + 0.6vw, 1.375rem) clamp(1.25rem, 1rem + 0.8vw, 1.75rem);
  border-radius: var(--radius-md);
  border-left: 4px solid var(--primary);
  font-family: var(--font-body);
  font-weight: 600;
  line-height: 1.55;
  box-shadow: var(--shadow-sm);
  animation: slide-in var(--dur-base) var(--ease-out);
}
/* Keep math legible and scaled with the step text */
.explanation-step .katex { font-size: 1.25em; }
.explanation-btn { width: 100%; }

/* ============================================================
   LOADING OVERLAY
   ============================================================ */
.loading-overlay {
  position: fixed;
  inset: 0;
  width: 100vw;
  height: 100vh;
  background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(4px);
  -webkit-backdrop-filter: blur(4px);
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  z-index: 10000;
}
.loading-overlay.visible { display: flex; animation: fade-in var(--dur-base) var(--ease-out); }
.loading-spinner {
  width: 3.75rem;
  height: 3.75rem;
  border: 5px solid color-mix(in srgb, var(--primary) 18%, transparent);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 1s linear infinite;
  margin-bottom: 1.25rem;
}
.loading-overlay p {
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary);
  letter-spacing: 0.02em;
  margin: 0;
  animation: pulse-bar 1.5s ease-in-out infinite;
}

/* ============================================================
   UPDATE BANNER
   ============================================================ */
.update-banner {
  position: fixed;
  left: 50%;
  bottom: calc(var(--space-5) + env(safe-area-inset-bottom, 0px));
  transform: translate(-50%, 16px);
  opacity: 0;
  display: flex;
  align-items: center;
  gap: var(--space-4);
  max-width: min(92vw, 34rem);
  padding: var(--space-3) var(--space-3) var(--space-3) var(--space-5);
  background: var(--surface);
  border: 1.5px solid var(--primary);
  border-radius: var(--radius-pill);
  box-shadow: var(--shadow-xl);
  z-index: 10001;
  pointer-events: auto;
  transition: opacity var(--dur-base) var(--ease-out),
              transform var(--dur-base) var(--ease-bounce);
}
.update-banner.show { opacity: 1; transform: translate(-50%, 0); }
.update-banner-text {
  font-family: var(--font-body);
  font-size: 0.9375rem;
  font-weight: 700;
  color: var(--text);
  line-height: 1.25;
}
.update-banner-btn {
  flex-shrink: 0;
  min-height: 40px;
  padding: 0.5rem 1.25rem;
  border: none;
  border-radius: var(--radius-pill);
  background: var(--primary);
  color: var(--text-on-accent);
  font-family: var(--font-display);
  font-size: 0.9375rem;
  font-weight: 800;
  letter-spacing: 0.02em;
  cursor: pointer;
  transition: background-color var(--dur-fast) var(--ease-out),
              transform var(--dur-fast) var(--ease-out);
}
.update-banner-btn:hover { background: var(--primary-hover); }
.update-banner-btn:active { transform: scale(0.96); }