/* ===========================================
   ikeda.simulator — monochrome learning UI
   =========================================== */

:root {
  --bg: #000;
  --fg: #fff;
  --dim: #c8c8c8;
  --dimmer: #666;
  --line: #333;
  --accent: #fff;
  --hud-bg: rgba(0, 0, 0, 0.92);
  --hud-w: 480px;
  --sans: "Pretendard Variable", "Pretendard", -apple-system, BlinkMacSystemFont,
    "Apple SD Gothic Neo", "Noto Sans KR", "Malgun Gothic", system-ui, sans-serif;
  --mono: "JetBrains Mono", "SF Mono", "Menlo", "Consolas", monospace;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html,
body {
  width: 100%;
  height: 100%;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--sans);
  font-size: 15px;
  overflow: hidden;
  -webkit-font-smoothing: antialiased;
  letter-spacing: 0;
  line-height: 1.6;
}

/* 데이터/숫자/라벨 — 모노스페이스 유지 */
.hud__title,
.hud__sub,
.hud__label,
.mode,
.ctrl__val,
.btn,
.wave,
.hud__meta,
.explain__ref,
.hud__keys {
  font-family: var(--mono);
  letter-spacing: 0.03em;
}

#stage {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  display: block;
  background: var(--bg);
  cursor: crosshair;
}

/* ============ HUD ============ */

.hud {
  position: fixed;
  top: 0;
  right: 0;
  width: var(--hud-w);
  height: 100vh;
  background: var(--hud-bg);
  border-left: 1px solid var(--line);
  padding: 24px 22px 20px 22px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  gap: 24px;
  backdrop-filter: blur(8px);
  z-index: 10;
  transition: transform 0.25s ease;
}

.hud--hidden {
  transform: translateX(100%);
}

.hud::-webkit-scrollbar {
  width: 4px;
}
.hud::-webkit-scrollbar-track {
  background: transparent;
}
.hud::-webkit-scrollbar-thumb {
  background: var(--dimmer);
}

.hud__header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--line);
}

.hud__title {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: lowercase;
}

.hud__tag {
  font-size: 14px;
  color: var(--dim);
  margin-top: 6px;
  letter-spacing: 0;
}

.hud__sub {
  font-size: 13px;
  color: var(--dim);
  font-variant-numeric: tabular-nums;
}

.hud__section {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.hud__section--explain {
  border: 1px solid var(--line);
  padding: 16px;
  background: rgba(255, 255, 255, 0.04);
}

.hud__label {
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--fg);
}

.hud__hint {
  font-size: 14px;
  color: var(--dim);
  line-height: 1.7;
}

/* ============ Mode buttons ============ */

.hud__modes {
  display: grid;
  grid-template-columns: 1fr;
  gap: 4px;
}

.mode {
  font-size: 14px;
  background: transparent;
  color: var(--fg);
  border: 1px solid var(--line);
  padding: 13px 16px;
  text-align: left;
  cursor: pointer;
  transition: background 0.1s, border-color 0.1s;
}

.mode:hover {
  border-color: var(--fg);
}

.mode.active {
  background: var(--fg);
  color: var(--bg);
  border-color: var(--fg);
}

/* ============ Explain panel ============ */

.explain__title {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0;
}

.explain__ref {
  font-size: 12px;
  color: var(--dim);
  margin-top: 4px;
  margin-bottom: 14px;
}

.explain__body {
  font-size: 15px;
  line-height: 1.75;
  color: #f0f0f0;
  margin-bottom: 16px;
}

.explain__principle {
  border-top: 1px dashed var(--line);
  padding-top: 14px;
}

.explain__subtitle {
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--fg);
  margin-bottom: 8px;
}

.explain__principle p {
  font-size: 14px;
  line-height: 1.75;
  color: var(--dim);
}

/* ============ Controls (sliders) ============ */

.hud__controls {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.ctrl {
  display: grid;
  grid-template-columns: 130px 1fr 80px;
  grid-template-rows: auto auto;
  align-items: center;
  gap: 6px 14px;
}

.ctrl__name {
  font-size: 15px;
  font-family: var(--mono);
  letter-spacing: 0.03em;
  text-transform: lowercase;
  color: var(--fg);
  font-weight: 700;
}

.ctrl__name em {
  display: block;
  font-style: normal;
  font-family: var(--sans);
  font-size: 13px;
  color: var(--dim);
  margin-top: 3px;
  font-weight: 400;
  letter-spacing: 0;
}

.ctrl input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  background: transparent;
  height: 18px;
  width: 100%;
  cursor: ew-resize;
}

.ctrl input[type="range"]::-webkit-slider-runnable-track {
  height: 2px;
  background: var(--dimmer);
}

.ctrl input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 12px;
  height: 18px;
  background: var(--fg);
  margin-top: -8px;
  border: none;
  border-radius: 0;
}

.ctrl input[type="range"]::-moz-range-track {
  height: 2px;
  background: var(--dimmer);
}

.ctrl input[type="range"]::-moz-range-thumb {
  width: 12px;
  height: 18px;
  background: var(--fg);
  border: none;
  border-radius: 0;
}

.ctrl__val {
  font-size: 14px;
  color: var(--fg);
  text-align: right;
  font-variant-numeric: tabular-nums;
  font-weight: 700;
}

.ctrl__desc {
  grid-column: 1 / -1;
  font-size: 13px;
  color: var(--dim);
  line-height: 1.65;
  padding-left: 0;
  margin-top: 4px;
}

/* ============ Audio controls ============ */

.hud__audio {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.btn {
  font-size: 14px;
  background: transparent;
  color: var(--fg);
  border: 1px solid var(--line);
  padding: 13px 16px;
  cursor: pointer;
  transition: background 0.1s, border-color 0.1s;
}

.btn:hover {
  border-color: var(--fg);
}

.btn.active {
  background: var(--fg);
  color: var(--bg);
}

.hud__wave {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 4px;
}

.wave {
  font-size: 13px;
  background: transparent;
  color: var(--fg);
  border: 1px solid var(--line);
  padding: 11px 4px;
  cursor: pointer;
  transition: background 0.1s, border-color 0.1s;
}

.wave:hover {
  border-color: var(--fg);
}

.wave.active {
  background: var(--fg);
  color: var(--bg);
}

/* ============ Footer ============ */

.hud__footer {
  margin-top: auto;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.hud__keys {
  font-size: 12px;
  color: var(--dim);
  line-height: 1.7;
}

.hud__meta {
  display: flex;
  justify-content: space-between;
  font-size: 13px;
  color: var(--fg);
  font-variant-numeric: tabular-nums;
}

/* ============ Overlay (start screen) ============ */

.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.92);
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: opacity 0.4s;
}

.overlay--hidden {
  opacity: 0;
  pointer-events: none;
}

.overlay__box {
  text-align: center;
  display: flex;
  flex-direction: column;
  gap: 14px;
  align-items: center;
  border: 1px solid var(--fg);
  padding: 40px 60px;
  max-width: 480px;
}

.overlay__title {
  font-size: 22px;
  font-weight: 700;
  letter-spacing: 0.1em;
}

.overlay__text {
  font-size: 12px;
  color: var(--fg);
  line-height: 1.6;
}

.overlay__text--small {
  font-size: 10px;
  color: var(--dim);
}

.overlay__btn {
  font-family: inherit;
  font-size: 12px;
  background: var(--fg);
  color: var(--bg);
  border: none;
  padding: 12px 32px;
  cursor: pointer;
  letter-spacing: 0.1em;
  margin-top: 8px;
}

.overlay__btn:hover {
  background: var(--dim);
}

/* ============ Responsive ============ */

@media (max-width: 768px) {
  :root {
    --hud-w: 100vw;
  }
  .hud {
    height: 50vh;
    top: auto;
    bottom: 0;
    border-left: none;
    border-top: 1px solid var(--line);
  }
}