:root {
  --colour-bg: #0a0b14;
  --colour-surface: #14162a;
  --colour-surface-alt: #1b1e3a;
  --colour-primary: #00e5ff;
  --colour-primary-dark: #00a8bf;
  --colour-accent: #ff2ec4;
  --colour-accent-dark: #c91d9b;
  --colour-text: #eef1ff;
  --colour-text-dim: #8d93c2;
  --colour-card-front: #14162a;
  --colour-card-back: #1b1e3a;
  --radius: 12px;
}

* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
}

body {
  margin: 0;
  font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  background: var(--colour-bg);
  color: var(--colour-text);
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  /* Stops iOS Safari treating rapid successive taps (eg on nav buttons) as a double-tap-to-zoom gesture. */
  touch-action: manipulation;
}

header {
  background: var(--colour-surface);
  color: var(--colour-text);
  padding: 0.75rem 1.5rem;
  text-align: center;
  display: flex;
  align-items: center;
  gap: 1rem;
  border-bottom: 2px solid var(--colour-primary);
  box-shadow: 0 0 6px rgba(0, 229, 255, 0.2);
}

.logo {
  height: 8rem;
  width: auto;
  flex-shrink: 0;
}

header .header-text {
  flex: 1;
  text-align: left;
}

header h1 {
  margin: 0;
  font-size: clamp(1.6rem, 3.5vw, 2.6rem);
  color: var(--colour-primary);
  text-shadow: 0 0 3px rgba(0, 229, 255, 0.35);
}

.header-subtitle {
  margin: 0.15rem 0 0;
  font-size: clamp(0.85rem, 1.4vw, 1.1rem);
  color: #ffe600;
}

.controls-bar {
  display: flex;
  flex-wrap: nowrap;
  justify-content: center;
  gap: 1rem;
  background: var(--colour-surface);
  padding: 0.85rem 1rem;
  border-bottom: 1px solid rgba(0, 229, 255, 0.3);
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.4);
}

.controls-bar label {
  display: flex;
  flex: 1 1 0;
  min-width: 0;
  max-width: 220px;
  flex-direction: column;
  gap: 0.25rem;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--colour-text-dim);
}

.controls-bar select {
  width: 100%;
  min-width: 0;
  padding: 0.45rem 0.6rem;
  font-size: 0.95rem;
  border: 1px solid var(--colour-primary);
  border-radius: 8px;
  background: var(--colour-surface-alt);
  color: var(--colour-text);
}

@media (max-width: 520px) {
  .controls-bar {
    gap: 0.5rem;
    padding: 0.6rem 0.5rem;
  }

  .controls-bar label {
    font-size: 0.7rem;
  }

  .controls-bar select {
    padding: 0.35rem 0.3rem;
    font-size: 0.8rem;
  }
}

main#app {
  flex: 1;
  min-height: 0;
  width: 100%;
  max-width: 1100px;
  margin: 0 auto;
  padding: 1.5rem 1rem 2rem;
  display: flex;
  flex-direction: column;
}

.screen {
  display: none;
  flex: 1;
  min-height: 0;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: 1rem;
}

.screen.active {
  display: flex;
}

.link-btn {
  border: none;
  background: none;
  color: var(--colour-accent);
  text-decoration: underline;
  cursor: pointer;
  font-size: 0.95rem;
  padding: 0.4rem;
  touch-action: manipulation;
}

@media (hover: hover) and (pointer: fine) {
  .link-btn:hover {
    color: var(--colour-accent-dark);
  }
}

.error-text {
  color: var(--colour-accent);
  font-weight: 600;
}

/* Card screen */

.section-tag {
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--colour-accent);
}

.progress {
  font-weight: 600;
  font-size: clamp(1rem, 1.6vw, 1.3rem);
  color: var(--colour-text-dim);
}

.card-scene {
  position: relative;
  width: 100%;
  max-width: 900px;
  min-height: 200px;
  max-height: 640px;
  flex: 1;
  perspective: 1400px;
}

.card {
  position: relative;
  width: 100%;
  height: 100%;
  border-radius: var(--radius);
  border: 1px solid var(--ring-colour, transparent);
  box-shadow: 0 0 10px var(--ring-colour, transparent);
  transform-style: preserve-3d;
  transition: transform 0.5s ease, border-color 0.3s ease, box-shadow 0.3s ease;
  cursor: pointer;
  touch-action: manipulation;
}

.card.revealed {
  transform: rotateY(180deg);
}

.card-face {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border-radius: var(--radius);
  border: 1px solid rgba(0, 229, 255, 0.4);
  box-shadow: 0 0 6px rgba(0, 229, 255, 0.12), 0 4px 14px rgba(0, 0, 0, 0.5);
  backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  padding: clamp(1.5rem, 3vw, 2.75rem);
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--colour-primary) transparent;
}

.card-face::-webkit-scrollbar {
  width: 8px;
}

.card-face::-webkit-scrollbar-track {
  background: transparent;
}

.card-face::-webkit-scrollbar-thumb {
  background-color: var(--colour-primary);
  border-radius: 4px;
}

.card-back::-webkit-scrollbar-thumb {
  background-color: var(--colour-accent);
}

.card-back {
  scrollbar-color: var(--colour-accent) transparent;
}

.card-front {
  background: var(--colour-card-front);
}

.card-back {
  background: var(--colour-card-back);
  transform: rotateY(180deg);
  border-color: rgba(255, 46, 196, 0.4);
  box-shadow: 0 0 6px rgba(255, 46, 196, 0.12), 0 4px 14px rgba(0, 0, 0, 0.5);
}

.card-label {
  font-size: clamp(0.85rem, 1.4vw, 1.1rem);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--colour-accent);
  font-weight: 700;
  margin-bottom: 0.75rem;
  text-shadow: 0 0 3px rgba(255, 46, 196, 0.3);
}

.card-text {
  font-size: clamp(1.15rem, 2.6vw, 2rem);
  line-height: 1.5;
  white-space: pre-wrap;
  text-align: center;
  margin: auto 0;
  color: var(--colour-text);
}

.controls {
  display: flex;
  gap: 0.6rem;
  flex-wrap: wrap;
  justify-content: center;
}

.controls button {
  width: clamp(9rem, 16vw, 11rem);
  padding: clamp(0.7rem, 1.2vw, 1rem) clamp(1.1rem, 2vw, 1.6rem);
  font-size: clamp(1rem, 1.4vw, 1.2rem);
  border: 1px solid var(--colour-primary);
  border-radius: var(--radius);
  cursor: pointer;
  background: transparent;
  color: var(--colour-primary);
  box-shadow: 0 0 10px rgba(0, 229, 255, 0.35);
  transition: background 0.15s ease, box-shadow 0.15s ease;
  touch-action: manipulation;
}

@media (hover: hover) and (pointer: fine) {
  .controls button:hover {
    background: rgba(0, 229, 255, 0.15);
    box-shadow: 0 0 16px rgba(0, 229, 255, 0.6);
  }
}

.controls button:disabled {
  border-color: var(--colour-text-dim);
  color: var(--colour-text-dim);
  box-shadow: none;
  cursor: not-allowed;
}

#btn-reveal {
  border-color: var(--colour-accent);
  color: var(--colour-accent);
  box-shadow: 0 0 10px rgba(255, 46, 196, 0.35);
}

@media (hover: hover) and (pointer: fine) {
  #btn-reveal:hover {
    background: rgba(255, 46, 196, 0.15);
    box-shadow: 0 0 16px rgba(255, 46, 196, 0.6);
  }
}

.secondary-controls {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  justify-content: center;
}

.about-row {
  display: flex;
  justify-content: center;
  margin-top: 0.25rem;
}

.about-btn {
  width: clamp(5rem, 9vw, 6rem);
  padding: 0.35rem 0.7rem;
  font-size: 0.8rem;
  border: 1px solid #ffe600;
  border-radius: var(--radius);
  cursor: pointer;
  background: transparent;
  color: #ffe600;
  box-shadow: 0 0 8px rgba(255, 230, 0, 0.35);
  transition: background 0.15s ease, box-shadow 0.15s ease;
  touch-action: manipulation;
}

@media (hover: hover) and (pointer: fine) {
  .about-btn:hover {
    background: rgba(255, 230, 0, 0.15);
    box-shadow: 0 0 14px rgba(255, 230, 0, 0.6);
  }
}

/* About modal */

.modal-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.65);
  align-items: center;
  justify-content: center;
  padding: 1rem;
  z-index: 100;
}

.modal-overlay.active {
  display: flex;
}

.modal-box {
  background: var(--colour-surface);
  border: 1px solid var(--colour-primary);
  border-radius: var(--radius);
  box-shadow: 0 0 20px rgba(0, 229, 255, 0.35);
  max-width: 560px;
  width: 100%;
  max-height: 85vh;
  overflow-y: auto;
  padding: 1.5rem 1.75rem;
  color: var(--colour-text);
}

.modal-box h2 {
  margin-top: 0;
  color: var(--colour-primary);
  text-shadow: 0 0 3px rgba(0, 229, 255, 0.35);
}

.modal-box p {
  line-height: 1.5;
}

.modal-box p a {
  color: var(--colour-primary);
}

.modal-box p a:hover,
.modal-box p a:focus-visible {
  color: var(--colour-accent);
}

.modal-checkbox-row {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.9rem;
  color: var(--colour-text-dim);
  margin: 1rem 0;
  cursor: pointer;
}

.modal-checkbox-row input[type="checkbox"] {
  -webkit-appearance: none;
  appearance: none;
  margin: 0;
  width: 1.2rem;
  height: 1.2rem;
  flex-shrink: 0;
  border: 2px solid var(--colour-primary);
  border-radius: 4px;
  background: transparent;
  cursor: pointer;
  position: relative;
}

.modal-checkbox-row input[type="checkbox"]:checked {
  background: var(--colour-primary);
}

/* Custom tick drawn with a rotated border, so its colour is consistent across
   browsers (iOS Safari otherwise renders the native tick white on cyan). */
.modal-checkbox-row input[type="checkbox"]:checked::after {
  content: '';
  position: absolute;
  left: 0.3rem;
  top: 0.05rem;
  width: 0.3rem;
  height: 0.55rem;
  border: solid var(--colour-bg);
  border-width: 0 2px 2px 0;
  transform: rotate(45deg);
}

.modal-close-btn {
  padding: 0.5rem 1.2rem;
  font-size: 1rem;
  border: 1px solid var(--colour-primary);
  border-radius: var(--radius);
  cursor: pointer;
  background: transparent;
  color: var(--colour-primary);
  box-shadow: 0 0 10px rgba(0, 229, 255, 0.35);
  touch-action: manipulation;
}

@media (hover: hover) and (pointer: fine) {
  .modal-close-btn:hover {
    background: rgba(0, 229, 255, 0.15);
    box-shadow: 0 0 16px rgba(0, 229, 255, 0.6);
  }
}

footer {
  text-align: center;
  padding: 0.6rem 1rem;
  font-size: 1.1rem;
}

footer a {
  color: var(--colour-text-dim);
  text-decoration: none;
}

@media (hover: hover) and (pointer: fine) {
  footer a:hover {
    color: var(--colour-accent);
  }
}