/* --- Buttons: offset-shadow, tactile press ---------------------------- */
.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-1);
  min-height: var(--touch-target-min);
  min-width: var(--touch-target-min);
  padding: var(--space-2) var(--space-4);
  border: 2px solid var(--color-ink);
  border-radius: var(--radius);
  background: var(--color-paper);
  color: var(--color-ink);
  font-family: var(--font-display);
  font-size: 1rem;
  cursor: pointer;
  box-shadow: var(--shadow-hard);
  transform: translate(0, 0);
  transition: transform 100ms ease, box-shadow 100ms ease;
  user-select: none;
}

.btn:hover { filter: brightness(0.97); }

.btn:focus-visible,
.free-text-input:focus-visible {
  outline: 3px solid var(--color-accent);
  outline-offset: 2px;
}

.btn:active,
.btn.is-pressed {
  transform: translate(
    calc(var(--shadow-offset) - var(--shadow-offset-pressed)),
    calc(var(--shadow-offset) - var(--shadow-offset-pressed))
  );
  box-shadow: var(--shadow-hard-pressed);
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  box-shadow: none;
  transform: none;
}

.btn-primary { background: var(--color-primary); color: white; border-color: var(--color-ink); }
.btn-accent { box-shadow: var(--shadow-hard-accent); }
.btn-accent:active { box-shadow: var(--shadow-offset-pressed) var(--shadow-offset-pressed) 0 0 var(--shadow-color-accent); }
.btn-ghost { background: transparent; box-shadow: none; border-color: transparent; }
.btn-ghost:active { transform: none; box-shadow: none; }
.btn-icon { padding: var(--space-2); }

.btn-hard { border-color: var(--color-red); }
.btn-medium { border-color: var(--color-ink); }
.btn-easy { border-color: var(--color-green); }

.btn.is-correct { animation: pulse-correct 420ms ease; }
.btn.is-wrong { animation: shake-wrong 380ms ease; }

@keyframes pulse-correct {
  0% { box-shadow: 0 0 0 0 rgba(0, 146, 69, 0.55); }
  60% { box-shadow: 0 0 0 10px rgba(0, 146, 69, 0); }
  100% { box-shadow: var(--shadow-hard); }
}

@keyframes shake-wrong {
  0%, 100% { transform: translate(0, 0); }
  20% { transform: translate(-6px, 0); }
  40% { transform: translate(5px, 0); }
  60% { transform: translate(-4px, 0); }
  80% { transform: translate(3px, 0); }
}

/* --- Cards -------------------------------------------------------------- */
.card {
  background: var(--color-paper);
  border: 2px solid var(--color-ink);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-hard-accent);
  padding: var(--space-4);
}

/* --- Modal ---------------------------------------------------------------*/
.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  padding: var(--space-3);
}

.modal {
  background: var(--color-paper);
  border: 2px solid var(--color-ink);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-hard);
  padding: var(--space-4);
  max-width: 420px;
  width: 100%;
}

/* --- Progress ring -------------------------------------------------------*/
.progress-ring { --ring-size: 96px; width: var(--ring-size); height: var(--ring-size); position: relative; }
.progress-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.progress-ring circle { fill: none; stroke-width: 10; }
.progress-ring .ring-bg { stroke: var(--color-paper-dim); }
.progress-ring .ring-fill {
  stroke: var(--color-primary);
  stroke-linecap: round;
  transition: stroke-dashoffset var(--transition-medium);
}
.progress-ring-label {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  font-weight: bold;
}

/* --- Streak --------------------------------------------------------------*/
.streak { display: inline-flex; align-items: center; gap: var(--space-1); font-weight: bold; }
.streak-flame { width: 24px; height: 24px; }
.streak.is-celebrating .streak-flame { animation: flame-pulse 650ms ease; }

@keyframes flame-pulse {
  0% { transform: scale(1) rotate(0); }
  40% { transform: scale(1.35) rotate(-6deg); }
  70% { transform: scale(1.1) rotate(4deg); }
  100% { transform: scale(1) rotate(0); }
}

.confetti-burst {
  position: fixed;
  pointer-events: none;
  z-index: 200;
}

/* --- Icon slot -------------------------------------------------------- */
.icon { width: var(--icon-size, 24px); height: var(--icon-size, 24px); display: inline-block; flex-shrink: 0; }

/* --- Bottom nav (mobile module switcher) --------------------------------*/
.bottom-nav {
  position: fixed;
  left: 0; right: 0; bottom: 0;
  display: flex;
  justify-content: space-around;
  background: var(--color-paper);
  border-top: 2px solid var(--color-ink);
  padding: var(--space-1) 0 calc(var(--space-1) + env(safe-area-inset-bottom));
  z-index: 40;
}

@media (min-width: 768px) {
  .bottom-nav { display: none; }
}

.bottom-nav-item {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  min-height: var(--touch-target-min);
  background: none;
  border: none;
  color: var(--color-muted);
  font-family: var(--font-display);
  font-size: 0.7rem;
  cursor: pointer;
}

.bottom-nav-item.is-active { color: var(--color-primary); }

.brand-link { display: inline-flex; align-items: center; }

/* --- App header ----------------------------------------------------------*/
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-3);
  border-bottom: 2px solid var(--color-ink);
}

.app-header .logo { height: 28px; }