:root {
  --bg: #1b1c22;
  --panel: #262832;
  --text: #eceef2;
  --muted: #9aa0ac;
  --accent: #5ec6ff;
  --accent-2: #ff9f5a;
  --good: #6ef59f;
  --bad: #ff5a5f;
  --white-key: #f7f7f5;
  --white-key-stroke: #2a2a2a;
  --black-key: #1c1c1c;
  --highlight: #ff7700;
  --highlight-secondary: #ff7700;
  --marker-root: #0055ff;
  --marker-default: #ffd166;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  padding: 24px;
}

header.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
  flex-wrap: wrap;
  gap: 12px;
}

header.site-header h1 {
  font-size: 1.4rem;
  margin: 0;
}

nav.site-nav a {
  color: var(--muted);
  text-decoration: none;
  margin-left: 16px;
  font-weight: 600;
}

nav.site-nav a.active,
nav.site-nav a:hover {
  color: var(--accent);
}

main {
  max-width: 1100px;
  margin: 0 auto;
}

.panel {
  background: var(--panel);
  border-radius: 12px;
  padding: 20px;
  margin-bottom: 20px;
}

.controls-row {
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  gap: 20px 28px;
  margin-bottom: 20px;
}

/* Last control row in a panel doesn't need trailing space before the
   panel's own bottom padding kicks in. */
.controls-row:last-child {
  margin-bottom: 0;
}

.controls-group {
  flex: 0 1 auto;
  min-width: 150px;
}

.controls-group-wide {
  flex: 0 1 auto;
  min-width: 260px;
}

.controls-group h3 {
  margin: 0 0 8px 0;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
}

/* Mode / quiz-type / difficulty rows: few items, so a wrapping flex
   row is fine - they rarely need more than one line. */
.mode-selector,
.quiz-type-toggle {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.difficulty-selector {
  width: min(100%, 320px);
}

.course-select {
  width: 100%;
  appearance: none;
  background: linear-gradient(180deg, #2d313c 0%, #232833 100%);
  color: var(--text);
  border: 1px solid #4e586a;
  border-radius: 10px;
  padding: 10px 42px 10px 12px;
  font: inherit;
  font-weight: 600;
  line-height: 1.3;
  box-shadow: inset 0 1px 0 rgba(255,255,255,0.04);
  background-image:
    linear-gradient(45deg, transparent 50%, var(--accent) 50%),
    linear-gradient(135deg, var(--accent) 50%, transparent 50%),
    linear-gradient(to right, transparent, transparent);
  background-position:
    calc(100% - 18px) calc(50% - 2px),
    calc(100% - 12px) calc(50% - 2px),
    100% 0;
  background-size: 6px 6px, 6px 6px, 2.5em 2.5em;
  background-repeat: no-repeat;
  cursor: pointer;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.course-select:hover,
.course-select:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(94, 198, 255, 0.15);
  outline: none;
}

.course-select option {
  background: #2d313c;
  color: var(--text);
  padding: 8px 10px;
}

.manual-config {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}

.manual-config-group {
  min-width: 180px;
  flex: 1 1 180px;
}

.manual-config-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
  margin-bottom: 8px;
}

#manual-key-container,
#manual-mode-container,
#manual-inversion-container {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.manual-toggle-btn {
  background: #33353f;
  color: var(--text);
  border: 1px solid #3f414c;
  border-radius: 8px;
  padding: 7px 10px;
  cursor: pointer;
  font-size: 0.82rem;
  transition: background 0.15s, border-color 0.15s, color 0.15s;
}

.manual-toggle-btn:hover {
  border-color: var(--accent);
}

.manual-toggle-btn.active {
  background: rgba(94, 198, 255, 0.18);
  border-color: var(--accent);
  color: var(--text);
  font-weight: 700;
}

/* Key selector: always 12 buttons. A fixed 6-column grid guarantees
   two clean rows of equal-width buttons, instead of flex-wrap
   breaking lines wherever the accumulated widths happen to overflow. */
.key-selector {
  display: grid;
  grid-template-columns: repeat(6, minmax(0, 1fr));
  gap: 6px;
}

/* Inversion selector: always 3 buttons with uneven label lengths
   ("Root Position" vs "1st Inversion"). A fixed 3-column grid forces
   them to the same width and keeps them on one row. */
.inversion-selector {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 6px;
}

.key-btn,
.mode-btn,
.inversion-btn,
.quiz-type-btn,
.difficulty-btn {
  background: #33353f;
  color: var(--text);
  border: 1px solid #3f414c;
  border-radius: 8px;
  padding: 8px 12px;
  cursor: pointer;
  font-size: 0.9rem;
  text-align: center;
  transition: background 0.15s, border-color 0.15s;
}

.key-btn:hover,
.mode-btn:hover,
.inversion-btn:hover,
.quiz-type-btn:hover,
.difficulty-btn:hover {
  border-color: var(--accent);
}

.key-btn.active,
.mode-btn.active,
.inversion-btn.active,
.quiz-type-btn.active,
.difficulty-btn.active {
  background: var(--accent);
  color: #10131a;
  border-color: var(--accent);
  font-weight: 700;
}

/* --- Stepper controls (octave transpose, keyboard range) --- */
/* Both octave-transpose.js and range-control.js render this same
   "◀ label ▶" shape via stepper.js, so they share one set of rules. */

.octave-transpose,
.range-control {
  display: flex;
  align-items: center;
  gap: 10px;
}

.octave-btn,
.range-btn {
  background: #33353f;
  color: var(--text);
  border: 1px solid #3f414c;
  border-radius: 8px;
  padding: 8px 14px;
  cursor: pointer;
  font-size: 1rem;
  transition: background 0.15s, border-color 0.15s;
}

.octave-btn:hover:not(:disabled),
.range-btn:hover:not(:disabled) {
  border-color: var(--accent-2);
}

.octave-btn:disabled,
.range-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.octave-label,
.range-label {
  min-width: 84px;
  text-align: center;
  font-weight: 700;
  color: var(--accent-2);
}

#current-selection {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--accent-2);
  margin-bottom: 16px;
}

.keyboard-scroll {
  overflow-x: auto;
  padding-bottom: 8px;
}

/* --- Keyboard rendering --- */

/* The SVG's viewBox defines its internal proportions; here we make it
   scale responsively to fill its container's width instead of staying
   at a fixed pixel size. Since it's a vector graphic, this stays sharp
   at any size and avoids the keyboard overflowing into a scrollbar on
   normal desktop widths. .keyboard-scroll's overflow-x: auto remains
   as a fallback only for very narrow (e.g. mobile) viewports.
   Note: deliberately no shape-rendering: crispEdges here - that
   disables anti-aliasing and looks jagged once the SVG is scaled to a
   non-1:1 size, which is the normal case for a responsive element.
   Default anti-aliased rendering scales smoothly at any size. */
.piano-keyboard {
  display: block;
  width: 100%;
  height: auto;
  max-width: 100%;
  cursor: pointer;
}

.key {
  stroke: var(--white-key-stroke);
  stroke-width: 1;
  vector-effect: non-scaling-stroke;
}

.key-white {
  fill: var(--white-key);
}

.key-black {
  fill: var(--black-key);
}

/* Style 1: whole-key-body highlight */
.key-white.key-highlighted {
  fill: var(--highlight);
}

.key-black.key-highlighted {
  fill: var(--highlight-secondary);
}

.key-white.key-highlighted-secondary {
  fill: var(--highlight-secondary);
}

/* Style 2: circle marker on top of a key */
.key-marker {
  stroke: #10131a;
  stroke-width: 1.5;
  vector-effect: non-scaling-stroke;
}

.marker-default {
  fill: var(--marker-default);
}

.marker-root {
  fill: var(--marker-root);
}

/* --- Home page --- */

.hero-panel {
  text-align: center;
  padding: 36px 20px;
}

.hero-title {
  margin: 0 0 10px 0;
  font-size: 1.6rem;
  color: var(--accent-2);
}

.hero-subtitle {
  margin: 0 auto;
  max-width: 640px;
  color: var(--muted);
}

.section-label {
  margin: 0 0 8px 0;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--muted);
}

.note-info {
  flex: 1 1 auto;
  font-weight: 700;
  color: var(--accent-2);
}

.page-links {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
}

.page-link-card {
  display: block;
  background: #33353f;
  border: 1px solid #3f414c;
  border-radius: 10px;
  padding: 16px;
  text-decoration: none;
  color: var(--text);
  transition: border-color 0.15s, transform 0.15s;
}

.page-link-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.page-link-card h3 {
  margin: 0 0 6px 0;
  color: var(--accent-2);
  font-size: 1rem;
}

.page-link-card p {
  margin: 0;
  color: var(--muted);
  font-size: 0.85rem;
  line-height: 1.4;
}

/* --- Quiz page --- */

.quiz-instructions {
  color: var(--muted);
  margin-top: 0;
}

.score-tracker {
  display: flex;
  gap: 14px;
  align-items: center;
  font-weight: 700;
  flex-wrap: wrap;
}

.score-correct { color: var(--good); }
.score-wrong { color: var(--bad); }
.score-accuracy { color: var(--muted); font-weight: 600; font-size: 0.85rem; }

.feedback-message {
  margin-top: 16px;
  padding: 10px 14px;
  border-radius: 8px;
  background: #33353f;
  color: var(--text);
  min-height: 2.7em;
  max-height: 2.7em;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  line-height: 1.2;
  overflow: hidden;
  white-space: nowrap;
}

.feedback-message.feedback-correct {
  background: rgba(0, 193, 71, 0.96);
  color: #ffffff;
  font-weight: 700;
  border: 1px solid rgba(120, 255, 171, 0.9);
}

.feedback-message.feedback-wrong {
  background: rgba(224, 0, 0, 0.749);
  color: #ffd4d4;
  font-weight: 700;
  border: 1px solid rgba(255, 114, 114, 0.8);
}

.quiz-actions {
  display: flex;
  gap: 12px;
  margin-top: 20px;
}

.primary-btn,
.secondary-btn {
  border: none;
  border-radius: 8px;
  padding: 10px 20px;
  font-size: 0.95rem;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.15s, opacity 0.15s;
}

.primary-btn {
  background: var(--accent);
  color: #10131a;
}

/* Same button, swapped to this style once it becomes "Next Question"
   after an answer has been submitted - a visual cue that its role
   changed without needing a second, separately-positioned button. */
.primary-btn.is-next {
  background: var(--accent-2);
}

.secondary-btn {
  background: var(--accent-2);
  color: #10131a;
}

.primary-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.hidden {
  display: none !important;
}

footer {
  text-align: center;
  color: var(--muted);
  font-size: 0.8rem;
  margin-top: 32px;
}