:root {
  --colour-body-bg: #F6F8FC;
  --colour-body-text: #1F2430;
  --colour-white: #FFFFFF;
  --colour-panel-bg: #FFFFFF;
  --colour-header-gradient-start: #002A48;
  --colour-header-gradient-end: #0072B5;
  --colour-header-icon: #E9E9E9;
  --shadow-light: rgba(17, 24, 39, 0.08);
  --shadow-medium: rgba(17, 24, 39, 0.18);
  --colour-border-light: #EDF0F4;
  --colour-border-standard: #E5E8F0;
  --colour-icon: #5B6473;
  --colour-heading: #002A48;
  --colour-info: #4B5563;
  --colour-placeholder: #94A3B8;
  --colour-hover-bg: #EEF2FF;
  --colour-active-bg: #DBEAFE;
  --colour-rationale-bg: #F5F7FF;
  --colour-rationale-border: #2563EB;
  --colour-unit-bg: #FBFCFF;
  --colour-success: #16A34A;
  --colour-danger: #DC2626;
  --font-family: "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --colour-body-bg: #0B1020;
    --colour-body-text: #E6EAF2;
    --colour-white: #FFFFFF;
    --colour-panel-bg: #111827;
    --colour-header-gradient-start: #001A2D;
    --colour-header-gradient-end: #06151D;
    --colour-header-icon: #BCBCBC;
    --shadow-light: rgba(0, 0, 0, 0.70);
    --shadow-medium: rgba(0, 0, 0, 0.90);
    --colour-border-light: #1F2937;
    --colour-border-standard: #2D3748;
    --colour-icon: #A0AEC0;
    --colour-heading: #FFFFFF;
    --colour-info: #CBD5E1;
    --colour-placeholder: #8A93A6;
    --colour-hover-bg: #1A2235;
    --colour-active-bg: #233B6E;
    --colour-rationale-bg: #0F1327;
    --colour-rationale-border: #5EA0FF;
    --colour-unit-bg: #131A2A;
    --colour-success: #008732;
    --colour-danger: #C73434;
  }
  img {
    filter: invert(1) hue-rotate(180deg) brightness(1.3) contrast(0.9);
  }
  #quiz-result {
    text-shadow: none !important;
  }
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  height: 100%;
  background-color: var(--colour-body-bg);
  color: var(--colour-body-text);
  font-family: var(--font-family);
  -webkit-tap-highlight-color: transparent;
}

header {
  background: linear-gradient( to right, var(--colour-header-gradient-start), var(--colour-header-gradient-end) );
  box-shadow: 0 2px 10px var(--shadow-light);
  padding: 0.4rem 0.5rem 0.3rem;
  text-align: center;
  margin-bottom: 0.6rem;
}

header h1 {
  margin: 0;
  font-size: 1.25rem;
  color: var(--colour-white);
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  cursor: pointer;
}

header h1 > span {
  display: flex;
  gap: 0.6rem;
}

header h1 .material-symbols-outlined {
  font-size: 1.6rem;
  color: var(--colour-header-icon);
}

header .subheader {
  font-weight: 500;
  color: var(--colour-header-icon);
  display: flex;
  align-items: center;
}

#curriculum-app {
  display: flex;
  max-width: 1200px;
  height: calc(100dvh - 90px);
  margin: 0 auto;
  gap: 1rem;
  padding: 0.4rem;
}

aside {
  flex: 0 0 352px;
  background-color: var(--colour-panel-bg);
  overflow-y: auto;
  box-shadow: 0 0 10px var(--shadow-medium);
}

#course-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.course-item {
  padding: 0.5rem 0.75rem;
  cursor: pointer;
  border-bottom: 1px solid var(--colour-border-light);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.course-item .material-symbols-outlined {
  font-size: 1.2rem;
  color: var(--colour-icon);
}

.course-item:hover {
  background: var(--colour-hover-bg);
}

.course-item.active {
  background: var(--colour-active-bg);
  font-weight: 600;
}

main {
  flex: 1;
  background-color: var(--colour-panel-bg);
  padding: 1.5rem;
  overflow-y: auto;
  position: relative;
  width: 100%;
  box-shadow: 0 0 10px var(--shadow-medium);
}

#course-detail,
#unit-detail,
#unit-quiz {
  display: none;
}

#course-detail.active,
#unit-detail.active,
#unit-quiz.active {
  display: block;
}

main h2 {
  margin-top: 0;
  font-size: 1.375rem;
  color: var(--colour-heading);
}

.course-info {
  margin: 1.4rem 0;
  line-height: 1.4;
  color: var(--colour-info);
}

.course-info b {
  color: var(--colour-heading);
  display: flex;
  align-items: center;
  gap: 0.3rem;
  margin-bottom: 0.3rem;
}

.course-info b .material-symbols-outlined {
  font-size: 1.1rem;
  color: var(--colour-info);
}

.course-placeholder {
  color: var(--colour-placeholder);
  font-size: 1rem;
  text-align: center;
}

.unit-rationale {
  margin: 1rem 0;
  padding: 0.6rem 1rem;
  background-color: var(--colour-rationale-bg);
  border-left: 4px solid var(--colour-rationale-border);
}

.unit-rationale p {
  margin: 0.6rem 0;
  display: inline-flex;
  align-items: start;
  gap: 0.5rem;
}

.unit-rationale .material-symbols-outlined {
  font-size: 1.1rem;
  color: var(--colour-info);
  position: relative;
  top: 4px;
}

h3 {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  margin: 1rem 0 0.75rem;
  padding-bottom: 0.25rem;
  font-size: 1.15rem;
  border-bottom: 2px solid var(--colour-heading);
  font-weight: normal;
  color: var(--colour-heading);
}

h3 .material-symbols-outlined {
  font-size: 1.3rem;
  color: var(--colour-info);
}

.units-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.unit-item {
  padding: 0.6rem;
  margin-bottom: 0.75rem;
  border: 2px solid var(--colour-border-standard);
  border-radius: 6px;
  background: var(--colour-unit-bg);
  cursor: pointer;
  display: flex;
  align-items: flex-start;
  gap: 0.4rem;
}

.unit-item > span:last-child {
  display: flex;
  flex-direction: column;
  gap: 0.2rem;
}

.unit-info .material-symbols-outlined {
  font-size: 1.1rem;
  color: var(--colour-icon);
}

.no-units {
  margin-bottom: 12px;
  color: var(--colour-placeholder);
}

.back-button {
  background: none;
  border: none;
  color: var(--colour-placeholder);
  cursor: pointer;
  font-size: 1rem;
  padding: 0;
  margin-bottom: 0.8rem;
}

#course-detail .back-button {
  display: none;
}

.key-knowledge-list {
  list-style: disc;
  padding-left: 1.5rem;
  margin: 0.5rem 0;
}

.key-knowledge-list li {
  margin-bottom: 0.75rem;
}

.key-knowledge-list li img {
  max-width: 100%;
  height: auto;
  display: block;
  margin-top: 0.5rem;
}

.loading {
  margin: 0.5rem 0;
}

#declarative-header-container {
  display: flex;
  align-items: center;
  gap: 1rem;
}

#declarative-header-container button {
  background: none;
  border: 2px solid var(--colour-border-standard);
  border-radius: 6px;
  color: var(--colour-placeholder);
  cursor: pointer;
  font-family: var(--font-family);
  font-size: 1rem;
  padding: 0.4rem 0.8rem 0.3rem;
  font-size: 0.9rem;
}

#declarative-header-container button:hover {
  box-shadow: 0 0 6px var(--shadow-light);
}

#unit-quiz h2 {
  text-align: center;
}

#question {
  margin: 2em;
  text-align: center;
  font-size: 14pt;
}

.answers {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2em;
  margin: 2em;
}

.answers button {
  background-color: var(--colour-body-bg);
  color: var(--colour-body-text);
  text-align: center;
  padding: 1em 2em;
  border: 3px solid var(--colour-border-light);
  font-family: var(--font-family);
  font-size: 14pt;
  border-radius: 1em;
  cursor: pointer;
  min-height: 5em;
  box-shadow: 0 0 6px var(--shadow-light);
}

.answers button:disabled {
  background-color: var(--colour-body-bg);
  color: var(--colour-body-text);
  cursor: default;
}

.answers button:not(:disabled):hover {
  box-shadow: 0 0 6px var(--shadow-medium);
}

#progress-container {
  width: 100%;
  background: var(--colour-border-light);
  border-radius: 4px;
  margin: 2em 0;
}

#progress {
  background: var(--colour-success);
  height: 20px;
  border-radius: 4px;
  width: 0%;
  transition: width 1s ease-in-out;
}

.answers button.correct {
  background-color: var(--colour-success);
  border: 3px solid var(--colour-success);
  box-shadow: 0 0 6px var(--colour-success);
  color: var(--colour-white);
}

.answers button.incorrect {
  background-color: var(--colour-danger);
  border: 3px solid var(--colour-danger);
  box-shadow: 0 0 6px var(--colour-danger);
  color: var(--colour-white);
}

.answers button.correct-outline {
  border: 3px solid var(--colour-success);
  box-shadow: 0 0 6px var(--colour-success);
}

#outcome {
  text-align: center;
  margin: 1em 1.2em 1em 1em;
  font-size: 20pt;
  font-weight: 500;
}

#outcome span {
  font-size: 32pt;
  position: relative;
  top: 12px;
  margin-right: 0.2em;
}

#quiz-result {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.5em;
  color: gold;
  text-shadow: 1px 0 1px var(--colour-info);
  text-align: center;
  padding: 1em;
}

#quiz-result .material-symbols-outlined {
  font-size: 120pt;
}

#quiz-result .congratulations {
  font-size: 32pt;
  font-weight: bold;
}

#quiz-result button {
  font-size: 16pt;
  font-family: var(--font-family);
  margin-top: 1.2em;
  color: var(--colour-placeholder);
  background: none;
  border: 2px solid var(--colour-border-standard);
  border-radius: 6px;
  padding: 0.4em 0.8em;
  cursor: pointer;
  box-shadow: 0 0 6px var(--shadow-light);
}

#quiz-result button:hover {
  box-shadow: 0 0 6px var(--shadow-medium);
}

@media (max-width: 1200px) {
  #curriculum-app {
    flex-direction: column;
  }

  aside {
    flex: 0 0 auto;
    width: 100%;
    height: calc(100dvh - 102px);
    display: none;
  }

  aside.active {
    display: block;
  }

  main {
    padding: 0.8rem;
    display: none;
  }

  main.active {
    display: block;
  }

  #course-detail .back-button {
    display: block;
  }

  .unit-item {
    padding: 0.5rem;
  }

  #progress-container {
    margin: 1.5em 0;
  }

  #question {
    margin: 1em;
  }

  .answers {
    grid-template-columns: 1fr;
    grid-template-rows: 1fr 1fr;
    gap: 1.5em;
    margin: 1.5em;
  }

  .answers button {
    padding: 0.5em 1em;
  }

  #outcome {
    margin: 1em;
    font-size: 16pt;
  }

  #quiz-result {
    padding: 0 1em;
  }

  #quiz-result .congratulations {
    font-size: 24pt;
  }
}

#celebration-overlay {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 9999;
  overflow: hidden;
}

#celebration-overlay.fade-out {
  animation: overlayFade 0.9s ease forwards;
}

@keyframes overlayFade {
  to { opacity: 0 }
}

.celebration-confetti {
  position: absolute;
  top: -10vh;
  width: var(--sz);
  height: var(--sz);
  background: hsl(var(--h) 90% 55%);
  transform: rotate(var(--rot));
  border-radius: var(--rad, 2px);
  box-shadow: 0 0 10px rgba(0,0,0,0.22);
  animation: confettiFall var(--dur) cubic-bezier(.2,.8,.2,1) var(--delay) forwards;
}

@keyframes confettiFall {
  0% { transform: translate3d(0, -10vh, 0) rotate(var(--rot)); opacity: 0 }
  12% { opacity: 1 }
  100% { transform: translate3d(var(--drift), 110vh, 0) rotate(900deg) }
}

.celebration-burst {
  position: absolute;
  width: 10px;
  height: 10px;
  transform: translate(-50%, -50%);
  animation: burstGlow 1.25s ease var(--delay) both;
  opacity: 0;
}

@keyframes burstGlow {
  0% { opacity: 0; filter: drop-shadow(0 0 0 hsla(var(--h) 90% 70%/.0)) }
  10% { opacity: 1 }
  35% { filter: drop-shadow(0 0 22px hsla(var(--h) 90% 70%/.75)) }
  100% { opacity: 0; filter: drop-shadow(0 0 0 hsla(var(--h) 90% 70%/.0)) }
}

.celebration-burst .spark {
  position: absolute;
  left: 0; top: 0;
  width: 6px; height: 6px;
  background: hsl(var(--h) 90% 60%);
  border-radius: 50%;
  transform-origin: 0 0;
  opacity: 0;
  animation: sparkFly 1.25s ease var(--delay) both;
}

@keyframes sparkFly {
  0% { transform: rotate(calc(var(--i) * 30deg)) translateX(0); opacity: 0 }
  8% { opacity: 1 }
  100% { transform: rotate(calc(var(--i) * 30deg)) translateX(140px); opacity: 0 }
}

.celebration-glow {
  position: absolute;
  inset: 0;
  background: radial-gradient(1200px 480px at 50% 60%, rgba(255,255,255,.22), transparent 60%);
  mix-blend-mode: screen;
  animation: glowPulse 2.2s ease-in-out 2 both;
}

@keyframes glowPulse {
  0%,100% { opacity: .2 }
  50% { opacity: .5 }
}