/* ============================================================
   FretWise — stylesheet
   Design tokens first, then base, layout, components.
   Dark, premium, blue accent. Degree colors are course-wide.
   ============================================================ */

/* ---------- 1. Tokens ---------- */
:root {
  /* canvas & surfaces */
  --bg: #0b0e14;
  --surface: #12161f;
  --surface-2: #171c27;
  --surface-3: #1e2432;
  --hairline: rgba(255,255,255,.08);
  --hairline-strong: rgba(255,255,255,.14);

  /* text */
  --text: #e8ecf4;
  --text-dim: #9aa3b5;
  --text-faint: #6b7385;

  /* accent */
  --accent: #4c8dff;
  --accent-soft: rgba(76,141,255,.14);
  --accent-strong: #6ea3ff;

  /* degree colors (course-wide contract) */
  --deg-root: #3b7dff;
  --deg-third: #35b979;
  --deg-fifth: #f08c3a;
  --deg-seventh: #a06bf0;
  --deg-ext: #e3c33e;
  --deg-other: #3a4356;

  /* fretboard */
  --board: #151a24;
  --fretwire: #333c4e;
  --nut: #c8cede;
  --string: #7c8699;
  --inlay: #2a3243;
  --key-white: #e9ecf3;
  --key-black: #232936;
  --key-border: #10141d;

  /* type scale */
  --fs-h1: clamp(1.7rem, 3.4vw, 2.35rem);
  --fs-h2: .78rem;
  --fs-h3: 1.12rem;
  --fs-body: 1rem;
  --fs-small: .85rem;

  /* spacing (8pt) */
  --s1: 8px; --s2: 16px; --s3: 24px; --s4: 32px; --s5: 48px; --s6: 64px;

  /* radii & shadow */
  --r-sm: 10px; --r-md: 16px; --r-lg: 22px;
  --shadow: 0 10px 30px rgba(0,0,0,.35);
  --sidebar-w: 300px;
}

/* ---------- 2. Base ---------- */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background:
    radial-gradient(1100px 500px at 85% -10%, rgba(76,141,255,.08), transparent 60%),
    var(--bg);
  color: var(--text);
  font: var(--fs-body)/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Inter, "Helvetica Neue", Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}
h1 { font-size: var(--fs-h1); line-height: 1.15; letter-spacing: -.02em; margin: var(--s1) 0 var(--s2); font-weight: 700; }
h3 { font-size: var(--fs-h3); margin: var(--s3) 0 var(--s1); font-weight: 650; }
p { margin: 0 0 var(--s2); color: var(--text); }
a { color: var(--accent-strong); text-decoration: none; }
strong { color: #fff; }
em { color: var(--text); }
button { font: inherit; cursor: pointer; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 6px; }
@media (prefers-reduced-motion: reduce) { *, *::before, *::after { animation: none !important; transition: none !important; } }

/* ---------- 3. Layout ---------- */
.app { display: grid; grid-template-columns: var(--sidebar-w) 1fr; height: 100dvh; }

.sidebar {
  display: flex; flex-direction: column;
  border-right: 1px solid var(--hairline);
  background: linear-gradient(180deg, rgba(23,28,39,.85), rgba(18,22,31,.95));
  backdrop-filter: blur(14px);
  overflow: hidden;
}
.brand { padding: var(--s3) var(--s3) var(--s2); display: flex; align-items: center; gap: 12px; }
.brand-mark { width: 34px; height: 34px; border-radius: 10px; flex: 0 0 auto;
  background: radial-gradient(circle at 50% 50%, var(--accent-strong) 0 34%, transparent 36%),
              linear-gradient(135deg, var(--accent), var(--accent-strong));
  box-shadow: 0 4px 14px rgba(76,141,255,.35); }
.progress-head { display: flex; justify-content: space-between; align-items: baseline; color: var(--text-dim); font-size: var(--fs-small); margin-bottom: 8px; }
.progress-head span:last-child { color: var(--text); font-variant-numeric: tabular-nums; }
.brand-name { font-weight: 750; font-size: 1.2rem; letter-spacing: -.01em; }
.brand-name span { color: var(--accent-strong); }
.brand-sub { color: var(--text-faint); font-size: var(--fs-small); margin-top: 2px; }

.progress-card { margin: 0 var(--s2) var(--s2); padding: var(--s2); background: var(--surface-2); border: 1px solid var(--hairline); border-radius: var(--r-md); }
.progress-track { height: 6px; background: var(--surface-3); border-radius: 99px; overflow: hidden; }
.progress-fill { height: 100%; width: 0; background: linear-gradient(90deg, var(--accent), var(--accent-strong)); border-radius: 99px; transition: width .5s cubic-bezier(.2,.8,.2,1); }
.progress-label { font-size: .78rem; color: var(--text-dim); margin-top: var(--s1); }

.nav { overflow-y: auto; padding: 0 var(--s2) var(--s4); flex: 1; scrollbar-width: thin; scrollbar-color: var(--surface-3) transparent; }
.nav-part { font-size: .7rem; text-transform: uppercase; letter-spacing: .12em; color: var(--text-faint); margin: var(--s3) var(--s1) var(--s1); font-weight: 650; }
.nav-item { display: flex; align-items: center; gap: 10px; padding: 8px 10px; border-radius: var(--r-sm); color: var(--text-dim); font-size: .92rem; transition: background .15s, color .15s; }
.nav-item:hover { background: var(--surface-3); color: var(--text); }
.nav-item.active { background: var(--accent-soft); color: var(--accent-strong); font-weight: 600; }
.nav-check { width: 18px; height: 18px; flex: none; border: 1.5px solid var(--hairline-strong); border-radius: 50%; font-size: 11px; display: grid; place-items: center; color: #fff; }
.nav-item.done .nav-check { background: var(--deg-third); border-color: var(--deg-third); }
.nav-title { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }

.main { overflow-y: auto; }
.lesson { max-width: 860px; margin: 0 auto; padding: var(--s5) var(--s4) var(--s6); }
.lesson-head { margin-bottom: var(--s4); }
.lesson-meta { color: var(--text-faint); font-size: var(--fs-small); }

.complete-btn { display: inline-flex; align-items: center; gap: 10px; padding: 9px 18px 9px 12px; border-radius: 99px; border: 1px solid var(--hairline-strong); background: var(--surface-2); color: var(--text-dim); transition: all .2s; }
.complete-btn:hover { border-color: var(--accent); color: var(--text); }
.complete-btn.is-done { background: rgba(53,185,121,.12); border-color: var(--deg-third); color: var(--deg-third); }
.cb-ring { width: 20px; height: 20px; border-radius: 50%; border: 1.5px solid currentColor; display: grid; place-items: center; font-size: 12px; }

/* ---------- 4. Lesson blocks ---------- */
.block { margin: var(--s4) 0; }
.block-label { font-size: var(--fs-h2); text-transform: uppercase; letter-spacing: .14em; color: var(--accent-strong); font-weight: 700; margin: 0 0 var(--s2); }

.objectives, .mistakes, .summary-list { margin: 0; padding: 0; list-style: none; display: grid; gap: 10px; }
.objectives li, .mistakes li, .summary-list li { padding: 12px 16px 12px 42px; background: var(--surface); border: 1px solid var(--hairline); border-radius: var(--r-md); position: relative; }
.objectives li::before { content: '◎'; position: absolute; left: 15px; color: var(--accent); }
.mistakes li::before { content: '✕'; position: absolute; left: 16px; color: var(--deg-fifth); font-weight: 700; }
.summary-list li::before { content: '✓'; position: absolute; left: 16px; color: var(--deg-third); font-weight: 700; }

.callout { padding: var(--s2) var(--s3); background: var(--accent-soft); border: 1px solid rgba(76,141,255,.3); border-radius: var(--r-md); margin: var(--s2) 0; }

.practice { padding: var(--s3); background: var(--surface); border: 1px solid var(--hairline); border-radius: var(--r-lg); }

/* figures & diagrams */
.fig { margin: var(--s3) 0; padding: var(--s3); background: var(--surface); border: 1px solid var(--hairline); border-radius: var(--r-lg); box-shadow: var(--shadow); overflow-x: auto; }
.fig figcaption { font-size: var(--fs-small); color: var(--text-dim); margin-bottom: var(--s2); }
.diagram { display: block; width: 100%; max-width: 760px; height: auto; margin: 0 auto; }
.cof { max-width: 440px; }

.svg-caption { fill: var(--text-faint); font-size: 12px; font-family: inherit; }
.svg-string { fill: var(--text-dim); font-size: 13px; font-weight: 600; font-family: inherit; }
.svg-note { fill: #fff; font-size: 12.5px; font-weight: 700; font-family: inherit; }
.svg-keylabel { fill: #59627a; font-size: 12px; font-family: inherit; }
.svg-body { fill: var(--text); font-size: 13.5px; font-family: inherit; }
.svg-step { font-size: 13px; font-weight: 700; font-family: inherit; }
.fb-note { cursor: pointer; }
.fb-note:hover circle:last-of-type, .fb-note:hover circle:only-of-type { filter: brightness(1.25); }

.cof-major { fill: var(--surface-3); stroke: var(--hairline-strong); transition: fill .15s; }
.cof-seg { cursor: pointer; }
.cof-seg:hover .cof-major { fill: var(--accent-soft); }
.cof-seg.sel .cof-major { fill: var(--accent); }
.svg-cof-major { fill: var(--text); font-size: 16px; font-weight: 700; font-family: inherit; pointer-events: none; }
.svg-cof-minor { fill: var(--text-dim); font-size: 12px; font-family: inherit; pointer-events: none; }
.svg-cof-center { fill: var(--text); font-size: 17px; font-weight: 750; font-family: inherit; }

/* legend dots */
.legend { display: flex; flex-wrap: wrap; gap: var(--s2); margin-top: var(--s2); font-size: var(--fs-small); color: var(--text-dim); }
.legend-item { display: inline-flex; align-items: center; gap: 7px; }
.dot { width: 12px; height: 12px; border-radius: 50%; display: inline-block; vertical-align: -1px; }
.dot-root { background: var(--deg-root); } .dot-third { background: var(--deg-third); }
.dot-fifth { background: var(--deg-fifth); } .dot-seventh { background: var(--deg-seventh); }
.dot-ext { background: var(--deg-ext); } .dot-other { background: var(--deg-other); }

/* tables */
.table-wrap { overflow-x: auto; margin: var(--s2) 0; border: 1px solid var(--hairline); border-radius: var(--r-md); }
table { width: 100%; border-collapse: collapse; font-size: .93rem; }
th { text-align: left; padding: 12px 16px; background: var(--surface-2); color: var(--text-dim); font-size: .78rem; text-transform: uppercase; letter-spacing: .08em; }
td { padding: 11px 16px; border-top: 1px solid var(--hairline); }
tbody tr:hover { background: rgba(255,255,255,.02); }

/* collapse + tooltip */
.collapse { margin: var(--s2) 0; border: 1px solid var(--hairline); border-radius: var(--r-md); background: var(--surface); overflow: hidden; }
.collapse summary { padding: 14px 18px; cursor: pointer; font-weight: 600; color: var(--accent-strong); list-style: none; }
.collapse summary::before { content: '▸ '; transition: transform .2s; display: inline-block; }
.collapse[open] summary::before { transform: rotate(90deg); }
.collapse-body { padding: 0 18px 14px; }

.tooltip { border-bottom: 1px dashed var(--accent); cursor: help; position: relative; }
.tooltip-body { position: absolute; left: 50%; bottom: calc(100% + 8px); transform: translateX(-50%); width: 240px; padding: 10px 14px; background: var(--surface-3); border: 1px solid var(--hairline-strong); border-radius: var(--r-sm); font-size: .84rem; color: var(--text-dim); opacity: 0; pointer-events: none; transition: opacity .15s; z-index: 5; box-shadow: var(--shadow); }
.tooltip:hover .tooltip-body, .tooltip:focus .tooltip-body { opacity: 1; }

/* quiz */
.quiz-item { padding: var(--s3); background: var(--surface); border: 1px solid var(--hairline); border-radius: var(--r-lg); margin-bottom: var(--s2); }
.quiz-q { font-weight: 600; }
.quiz-opts { display: grid; gap: 10px; }
.quiz-opt { text-align: left; padding: 12px 16px; border-radius: var(--r-sm); border: 1px solid var(--hairline-strong); background: var(--surface-2); color: var(--text); transition: border-color .15s, background .15s; }
.quiz-opt:hover:not(:disabled) { border-color: var(--accent); }
.quiz-opt.correct { background: rgba(53,185,121,.15); border-color: var(--deg-third); }
.quiz-opt.wrong { background: rgba(199,60,74,.15); border-color: #c73c4a; }
.quiz-why { margin: var(--s2) 0 0; color: var(--text-dim); font-size: .92rem; padding-left: 14px; border-left: 2px solid var(--accent); }
.hidden { display: none; }

/* flashcards */
.flashdeck { max-width: 460px; }
.flashcard { position: relative; height: 150px; perspective: 900px; cursor: pointer; }
.fc-face { position: absolute; inset: 0; display: grid; place-items: center; padding: var(--s3); text-align: center; font-weight: 600; background: var(--surface-2); border: 1px solid var(--hairline-strong); border-radius: var(--r-lg); backface-visibility: hidden; transition: transform .5s cubic-bezier(.2,.8,.2,1); }
.fc-back { transform: rotateY(180deg); background: var(--accent-soft); border-color: rgba(76,141,255,.35); }
.flashcard.flipped .fc-front { transform: rotateY(180deg); }
.flashcard.flipped .fc-back { transform: rotateY(360deg); }
.fc-controls { display: flex; align-items: center; justify-content: center; gap: var(--s2); margin-top: var(--s2); color: var(--text-dim); font-size: var(--fs-small); }
.btn-ghost { background: var(--surface-2); border: 1px solid var(--hairline-strong); color: var(--text); border-radius: var(--r-sm); padding: 6px 14px; }
.btn-ghost:hover { border-color: var(--accent); }

/* lesson footer nav */
.lesson-nav { display: grid; grid-template-columns: 1fr 1fr; gap: var(--s2); margin-top: var(--s5); }
.lnav { display: flex; flex-direction: column; gap: 4px; padding: var(--s2) var(--s3); border: 1px solid var(--hairline); border-radius: var(--r-md); background: var(--surface); transition: border-color .15s, transform .15s; }
.lnav:hover { border-color: var(--accent); transform: translateY(-2px); }
.lnav span { font-size: .78rem; color: var(--text-faint); }
.lnav strong { color: var(--text); }
.lnav-next { text-align: right; }

/* mobile */
.nav-toggle { display: none; position: fixed; top: 14px; left: 14px; z-index: 30; width: 44px; height: 44px; border-radius: 12px; background: var(--surface-2); border: 1px solid var(--hairline-strong); color: var(--text); font-size: 20px; }
.scrim { display: none; }

@media (max-width: 900px) {
  .app { grid-template-columns: 1fr; }
  .sidebar { position: fixed; inset: 0 auto 0 0; width: min(320px, 86vw); z-index: 25; transform: translateX(-105%); transition: transform .3s cubic-bezier(.2,.8,.2,1); box-shadow: var(--shadow); }
  body.nav-open .sidebar { transform: translateX(0); }
  .nav-toggle { display: block; }
  body.nav-open .scrim { display: block; position: fixed; inset: 0; background: rgba(0,0,0,.5); z-index: 20; }
  .lesson { padding: var(--s6) var(--s2) var(--s5); }
  .lesson-nav { grid-template-columns: 1fr; }
}