:root {
  --duo-green: #58cc02;
  --duo-green-dark: #4caf00;
  --duo-blue: #1cb0f6;
  --duo-blue-dark: #1899d6;
  --duo-red: #ff4b4b;
  --duo-red-dark: #ea2b2b;
  --duo-yellow: #ffc800;
  --duo-text: #3c3c3c;
  --duo-gray: #777777;
  --duo-gray-light: #afafaf;
  --duo-border: #e5e5e5;
  --duo-bg: #f7f7f7;
  --duo-surface: #ffffff;
  --duo-surface-hover: #f0faff;
  --duo-chip-selected-bg: #e7f7ff;
  --duo-correct-bg: #d7ffb8;
  --duo-incorrect-bg: #ffdfe0;
  --duo-option-correct-bg: #ecfce2;
  --duo-option-incorrect-bg: #ffeaea;
}

[data-theme="dark"] {
  --duo-text: #e8e8e8;
  --duo-gray: #aaaaaa;
  --duo-gray-light: #666666;
  --duo-border: #333333;
  --duo-bg: #1a1a2e;
  --duo-surface: #16213e;
  --duo-surface-hover: #1a2a4a;
  --duo-chip-selected-bg: #1a3a5c;
  --duo-correct-bg: #1a3d1a;
  --duo-incorrect-bg: #3d1a1a;
  --duo-option-correct-bg: #1a3d1a;
  --duo-option-incorrect-bg: #3d1a1a;
}

* {
  box-sizing: border-box;
}

body {
  background: var(--duo-bg);
  font-family: "Nunito", sans-serif;
  color: var(--duo-text);
  transition: background-color 0.3s ease, color 0.3s ease;
}

.font-display {
  font-family: "Baloo 2", sans-serif;
  font-weight: 700;
}

.font-body {
  font-family: "Nunito", sans-serif;
}

.text-duo-text { color: var(--duo-text); }
.text-duo-gray { color: var(--duo-gray); }
.text-duo-gray-light { color: var(--duo-gray-light); }
.text-duo-green { color: var(--duo-green); }
.text-duo-blue { color: var(--duo-blue); }
.text-duo-red { color: var(--duo-red); }
.bg-duo-green { background-color: var(--duo-green); }
.bg-duo-border { background-color: var(--duo-border); }

.duo-transition {
  transition: width 0.35s ease;
}

@media (prefers-reduced-motion: reduce) {
  * {
    animation-duration: 0.001ms !important;
    transition-duration: 0.001ms !important;
  }
}


/* ---------- Inputs ---------- */
.duo-input {
  width: 100%;
  font-family: "Nunito", sans-serif;
  font-weight: 700;
  font-size: 1rem;
  color: var(--duo-text);
  background: var(--duo-surface);
  border: 2px solid var(--duo-border);
  border-radius: 14px;
  padding: 0.85rem 1rem;
  outline: none;
  transition: border-color 0.15s ease, background-color 0.3s ease;
}

.duo-input:focus {
  border-color: var(--duo-blue);
}

.duo-input:focus-visible {
  outline: 2px solid var(--duo-blue);
  outline-offset: 2px;
}

/* ---------- Chunky 3D buttons (signature element) ---------- */
.duo-btn {
  font-family: "Baloo 2", sans-serif;
  font-weight: 700;
  letter-spacing: 0.03em;
  font-size: 1rem;
  padding: 0.95rem 1.5rem;
  border-radius: 16px;
  border: none;
  cursor: pointer;
  transition: transform 0.05s ease, box-shadow 0.05s ease, background-color 0.15s ease;
  color: #ffffff;
}

.duo-btn:focus-visible {
  outline: 3px solid var(--duo-blue);
  outline-offset: 3px;
}

.duo-btn:disabled {
  cursor: not-allowed;
  opacity: 0.6;
}

.duo-btn-green {
  background: var(--duo-green);
  box-shadow: 0 4px 0 var(--duo-green-dark);
}
.duo-btn-green:not(:disabled):hover { background: #63d904; }
.duo-btn-green:not(:disabled):active {
  transform: translateY(4px);
  box-shadow: 0 0 0 var(--duo-green-dark);
}

.duo-btn-blue {
  background: var(--duo-blue);
  box-shadow: 0 4px 0 var(--duo-blue-dark);
}
.duo-btn-blue:not(:disabled):hover { background: #29baff; }
.duo-btn-blue:not(:disabled):active {
  transform: translateY(4px);
  box-shadow: 0 0 0 var(--duo-blue-dark);
}

.duo-btn-red {
  background: var(--duo-red);
  box-shadow: 0 4px 0 var(--duo-red-dark);
}

.duo-btn-gray {
  background: var(--duo-gray-light);
  box-shadow: 0 4px 0 #969696;
}

/* ---------- Quantity chips ---------- */
.duo-qty-chip {
  font-family: "Baloo 2", sans-serif;
  font-weight: 700;
  font-size: 0.9rem;
  min-width: 44px;
  padding: 0.5rem 0.75rem;
  border-radius: 12px;
  border: 2px solid var(--duo-border);
  background: var(--duo-surface);
  color: var(--duo-text);
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}
.duo-qty-chip:hover:not(:disabled) {
  border-color: var(--duo-blue);
  background: var(--duo-surface-hover);
}
.duo-qty-chip:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}
.duo-qty-chip:focus-visible {
  outline: 2px solid var(--duo-blue);
  outline-offset: 2px;
}

/* ---------- Stepper ---------- */
.duo-stepper-btn {
  width: 44px;
  height: 44px;
  border-radius: 12px;
  border: 2px solid var(--duo-border);
  background: var(--duo-surface);
  font-family: "Baloo 2", sans-serif;
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--duo-text);
  cursor: pointer;
  transition: border-color 0.15s ease, transform 0.05s ease;
}
.duo-stepper-btn:hover { border-color: var(--duo-blue); }
.duo-stepper-btn:active { transform: scale(0.95); }
.duo-stepper-btn:focus-visible {
  outline: 2px solid var(--duo-blue);
  outline-offset: 2px;
}

/* ---------- Category chips ---------- */
.duo-chip {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.75rem 0.9rem;
  border: 2px solid var(--duo-border);
  border-radius: 14px;
  background: var(--duo-surface);
  cursor: pointer;
  font-family: "Nunito", sans-serif;
  font-weight: 700;
  font-size: 0.85rem;
  color: var(--duo-text);
  transition: border-color 0.15s ease, background-color 0.15s ease;
  user-select: none;
}
.duo-chip:hover { border-color: var(--duo-blue); }
.duo-chip.selected {
  border-color: var(--duo-blue);
  background: var(--duo-chip-selected-bg);
  color: var(--duo-blue);
}
.duo-chip input {
  position: absolute;
  opacity: 0;
  width: 0;
  height: 0;
}
.duo-chip:focus-within {
  outline: 2px solid var(--duo-blue);
  outline-offset: 2px;
}

/* ---------- Report button ---------- */
.duo-report-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.25rem;
  font-family: "Nunito", sans-serif;
  font-weight: 700;
  font-size: 0.8rem;
  color: var(--duo-gray);
  background: none;
  border: 2px solid var(--duo-border);
  border-radius: 10px;
  padding: 0.45rem 0.75rem;
  cursor: pointer;
  transition: border-color 0.15s ease, color 0.15s ease;
}
.duo-report-btn:hover:not(:disabled) {
  border-color: var(--duo-red);
  color: var(--duo-red);
}
.duo-report-btn:disabled {
  cursor: default;
  opacity: 0.6;
}
.duo-report-btn:focus-visible {
  outline: 2px solid var(--duo-red);
  outline-offset: 2px;
}

/* ---------- Answer options ---------- */
.duo-option {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  width: 100%;
  text-align: left;
  padding: 0.9rem 1.1rem;
  border: 2px solid var(--duo-border);
  border-radius: 14px;
  background: var(--duo-surface);
  font-family: "Nunito", sans-serif;
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--duo-text);
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease, transform 0.05s ease;
}
.duo-option:hover:not(:disabled) { border-color: var(--duo-blue-dark); background: var(--duo-surface-hover); }
.duo-option:active:not(:disabled) { transform: scale(0.99); }
.duo-option:focus-visible {
  outline: 2px solid var(--duo-blue);
  outline-offset: 2px;
}
.duo-option:disabled { cursor: default; }

.duo-option.selected {
  border-color: var(--duo-blue);
  background: var(--duo-chip-selected-bg);
  color: var(--duo-blue);
}
.duo-option.correct {
  border-color: var(--duo-green);
  background: var(--duo-option-correct-bg);
  color: var(--duo-green);
}
.duo-option.incorrect {
  border-color: var(--duo-red);
  background: var(--duo-option-incorrect-bg);
  color: var(--duo-red);
}

.duo-option-mark {
  width: 22px;
  height: 22px;
  border-radius: 999px;
  border: 2px solid var(--duo-border);
  flex-shrink: 0;
}
.duo-option.selected .duo-option-mark { border-color: var(--duo-blue); background: var(--duo-blue); }
.duo-option.correct .duo-option-mark { border-color: var(--duo-green); background: var(--duo-green); }
.duo-option.incorrect .duo-option-mark { border-color: var(--duo-red); background: var(--duo-red); }

/* ---------- Action bar (signature element) ---------- */
.duo-action-bar {
  border-top: 2px solid var(--duo-border);
  background: var(--duo-surface);
  transition: background-color 0.2s ease, border-color 0.2s ease;
}
.duo-action-bar.state-correct {
  background: var(--duo-correct-bg);
  border-top-color: var(--duo-correct-bg);
}
.duo-action-bar.state-incorrect {
  background: var(--duo-incorrect-bg);
  border-top-color: var(--duo-incorrect-bg);
}

/* ---------- Cards ---------- */
.duo-card {
  background: var(--duo-surface);
  border: 2px solid var(--duo-border);
  border-radius: 18px;
  padding: 1.25rem;
  transition: background-color 0.3s ease, border-color 0.3s ease;
}

/* ---------- Category result bar ---------- */
.duo-cat-bar-track {
  height: 10px;
  border-radius: 999px;
  background: var(--duo-border);
  overflow: hidden;
}
.duo-cat-bar-fill {
  height: 100%;
  border-radius: 999px;
}

.screen {
  animation: duo-fade-in 0.25s ease;
}
@keyframes duo-fade-in {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: translateY(0); }
}

/* ---------- Modal ---------- */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(0, 0, 0, 0.4);
  backdrop-filter: blur(4px);
}

.modal-content {
  background: var(--duo-surface);
  border: 2px solid var(--duo-border);
  border-radius: 18px;
  padding: 2rem;
  width: 90%;
  max-width: 360px;
  box-shadow: 0 12px 40px rgba(0, 0, 0, 0.2);
}

/* ---------- Custom scrollbars ---------- */
::-webkit-scrollbar {
  width: 6px;
}
::-webkit-scrollbar-track {
  background: transparent;
}
::-webkit-scrollbar-thumb {
  background: var(--duo-border);
  border-radius: 999px;
}
::-webkit-scrollbar-thumb:hover {
  background: var(--duo-gray-light);
}

/* Firefox */
* {
  scrollbar-width: thin;
  scrollbar-color: var(--duo-border) transparent;
}

/* ---------- Study links ---------- */
.study-link-item {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.6rem 0.75rem;
  border-radius: 10px;
  background: var(--duo-bg);
  border: 1px solid var(--duo-border);
  text-decoration: none;
  transition: border-color 0.15s ease, background-color 0.15s ease, transform 0.05s ease;
}
.study-link-item:hover {
  border-color: var(--duo-blue);
  background: var(--duo-surface-hover);
  transform: translateX(2px);
}
.study-link-item:focus-visible {
  outline: 2px solid var(--duo-blue);
  outline-offset: 2px;
}

.study-link-badge {
  flex-shrink: 0;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--duo-red);
  color: #ffffff;
  font-family: "Baloo 2", sans-serif;
  font-weight: 700;
  font-size: 0.7rem;
  display: flex;
  align-items: center;
  justify-content: center;
}

.study-link-title {
  flex: 1;
  font-family: "Nunito", sans-serif;
  font-weight: 700;
  font-size: 0.78rem;
  color: var(--duo-text);
  line-height: 1.3;
  overflow: hidden;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
}

.study-link-arrow {
  flex-shrink: 0;
  font-size: 0.85rem;
  color: var(--duo-gray-light);
  transition: color 0.15s ease;
}
.study-link-item:hover .study-link-arrow {
  color: var(--duo-blue);
}