/* ==========================================================================
   Muga (無我) — Minimal Meditative Web Application
   Philosophy: "Nothing to achieve. Simply surrender to sound."
   ========================================================================== */

/* --------------------------------------------------------------------------
   CSS Custom Properties (Design Tokens)
   -------------------------------------------------------------------------- */
:root {
  --color-bg: #08090b;
  --color-bg-surface: rgba(255, 255, 255, 0.03);
  --color-text-main: #e6e8ec;
  --color-text-muted: #8b909c;
  --color-text-dim: #545864;
  --color-border: rgba(255, 255, 255, 0.1);
  --color-border-hover: rgba(255, 255, 255, 0.22);
  --color-focus: rgba(230, 232, 236, 0.7);

  --font-serif: "Shippori Mincho", "Yu Mincho", "Hiragino Mincho ProN", "Source Han Serif", "Noto Serif JP", serif;
  --font-sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", sans-serif;

  --transition-gentle: 0.8s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-fast: 0.3s ease;
}

/* --------------------------------------------------------------------------
   Reset & Base Styles
   -------------------------------------------------------------------------- */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  background-color: var(--color-bg);
  color: var(--color-text-main);
  font-family: var(--font-serif);
  font-size: 16px;
  line-height: 1.8;
  letter-spacing: 0.08em;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  scroll-behavior: smooth;
  height: 100%;
}

body {
  background-color: var(--color-bg);
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  align-items: center;
  position: relative;
  overflow-x: hidden;
  padding: max(1.5rem, env(safe-area-inset-top))
           max(1.5rem, env(safe-area-inset-right))
           max(1.5rem, env(safe-area-inset-bottom))
           max(1.5rem, env(safe-area-inset-left));
}

/* --------------------------------------------------------------------------
   Subtle Ambient Background (Breathing Light)
   -------------------------------------------------------------------------- */
.ambient-glow {
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: min(75vw, 600px);
  height: min(75vw, 600px);
  background: radial-gradient(
    circle,
    rgba(255, 255, 255, 0.035) 0%,
    rgba(255, 255, 255, 0.01) 45%,
    rgba(8, 9, 11, 0) 70%
  );
  border-radius: 50%;
  pointer-events: none;
  z-index: 0;
  opacity: 0.7;
  animation: gentleBreath 12s ease-in-out infinite;
}

@keyframes gentleBreath {
  0%, 100% {
    transform: translate(-50%, -50%) scale(0.96);
    opacity: 0.55;
  }
  50% {
    transform: translate(-50%, -50%) scale(1.04);
    opacity: 0.85;
  }
}

/* --------------------------------------------------------------------------
   Top Bar (Quiet brand indicator & return link)
   -------------------------------------------------------------------------- */
.app-header {
  width: 100%;
  max-width: 800px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  z-index: 2;
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  letter-spacing: 0.12em;
  color: var(--color-text-dim);
}

.back-link {
  color: var(--color-text-dim);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.4rem 0.6rem;
  border-radius: 4px;
  transition: color var(--transition-fast), opacity var(--transition-fast);
}

.back-link:hover,
.back-link:focus-visible {
  color: var(--color-text-muted);
}

.app-indicator {
  opacity: 0.7;
  text-transform: uppercase;
}

/* --------------------------------------------------------------------------
   Main Container & Sections
   -------------------------------------------------------------------------- */
.main-stage {
  width: 100%;
  max-width: 640px;
  flex: 1;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  text-align: center;
  position: relative;
  z-index: 2;
  padding: 2.5rem 1rem;
}

/* Section transitions */
.scene {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  width: 100%;
  opacity: 0;
  transform: translateY(8px);
  transition: opacity var(--transition-gentle), transform var(--transition-gentle);
  pointer-events: none;
}

.scene.active {
  display: flex;
  opacity: 1;
  transform: translateY(0);
  pointer-events: auto;
}

/* --------------------------------------------------------------------------
   Enso Emblem (Mindful Circle)
   -------------------------------------------------------------------------- */
.enso-container {
  margin-bottom: 2.2rem;
  width: 130px;
  height: 130px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

.enso-svg {
  width: 100%;
  height: 100%;
  filter: drop-shadow(0 0 16px rgba(255, 255, 255, 0.05));
  transition: transform var(--transition-gentle);
}

.playing .enso-svg {
  animation: ensoPulse 8s ease-in-out infinite;
}

@keyframes ensoPulse {
  0%, 100% {
    transform: scale(1);
    opacity: 0.85;
  }
  50% {
    transform: scale(1.05);
    opacity: 1;
  }
}

/* --------------------------------------------------------------------------
   Typography
   -------------------------------------------------------------------------- */
.app-title {
  font-size: 2.75rem;
  font-weight: 400;
  letter-spacing: 0.25em;
  margin-bottom: 0.6rem;
  color: var(--color-text-main);
  text-indent: 0.25em; /* Optical centering for spaced text */
}

.app-subtext {
  font-size: 1.0625rem;
  font-weight: 400;
  color: var(--color-text-muted);
  letter-spacing: 0.15em;
  margin-bottom: 2.5rem;
}

.guidance-box {
  margin-top: 2.5rem;
  max-width: 480px;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.guidance-text {
  font-size: 0.9375rem;
  color: var(--color-text-dim);
  letter-spacing: 0.1em;
  line-height: 1.9;
}

/* Playing Scene Typography */
.playing-message {
  font-size: 1.25rem;
  font-weight: 400;
  color: var(--color-text-main);
  letter-spacing: 0.16em;
  line-height: 2;
  margin-bottom: 0.8rem;
}

.playing-submessage {
  font-size: 0.9375rem;
  color: var(--color-text-muted);
  letter-spacing: 0.12em;
  margin-bottom: 2.5rem;
}

/* Ended Scene Typography */
.ended-message {
  font-size: 1.35rem;
  font-weight: 400;
  color: var(--color-text-main);
  letter-spacing: 0.18em;
  margin-bottom: 0.8rem;
}

.ended-submessage {
  font-size: 0.95rem;
  color: var(--color-text-muted);
  letter-spacing: 0.14em;
  margin-bottom: 2.5rem;
}

/* Status announcements (accessible live region) */
.visually-hidden {
  position: absolute !important;
  width: 1px !important;
  height: 1px !important;
  padding: 0 !important;
  margin: -1px !important;
  overflow: hidden !important;
  clip: rect(0, 0, 0, 0) !important;
  white-space: nowrap !important;
  border: 0 !important;
}

/* --------------------------------------------------------------------------
   Controls & Buttons
   -------------------------------------------------------------------------- */
.primary-btn {
  appearance: none;
  background: var(--color-bg-surface);
  color: var(--color-text-main);
  border: 1px solid var(--color-border);
  border-radius: 9999px;
  font-family: var(--font-serif);
  font-size: 1rem;
  letter-spacing: 0.2em;
  padding: 0.95rem 2.8rem;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  transition: all var(--transition-fast);
  min-height: 48px;
  min-width: 48px;
  text-indent: 0.2em; /* Optical centering */
}

.primary-btn:hover {
  background: rgba(255, 255, 255, 0.08);
  border-color: var(--color-border-hover);
  color: #ffffff;
  transform: translateY(-1px);
}

.primary-btn:active {
  transform: translateY(0);
  background: rgba(255, 255, 255, 0.05);
}

.primary-btn:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 4px;
}

.primary-btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
  transform: none;
}

/* Playing Scene Action Controls */
.playing-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 1.5rem;
  margin-top: 1rem;
  margin-bottom: 2rem;
}

.control-btn {
  appearance: none;
  background: transparent;
  color: var(--color-text-dim);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 50%;
  width: 52px;
  height: 52px;
  min-width: 48px;
  min-height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.control-btn svg {
  width: 20px;
  height: 20px;
  fill: currentColor;
  transition: fill var(--transition-fast);
}

.control-btn:hover {
  color: var(--color-text-muted);
  border-color: var(--color-border);
  background: rgba(255, 255, 255, 0.04);
}

.control-btn:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 4px;
}

/* --------------------------------------------------------------------------
   Volume Controller
   -------------------------------------------------------------------------- */
.volume-panel {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.75rem;
  color: var(--color-text-dim);
  margin-top: 2rem;
  opacity: 0.65;
  transition: opacity var(--transition-fast);
}

.playing .volume-panel {
  opacity: 0.28;
}

.volume-panel:hover,
.volume-panel:focus-within {
  opacity: 1 !important;
}

.volume-icon-btn {
  background: transparent;
  border: none;
  color: inherit;
  cursor: pointer;
  padding: 0.35rem;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 4px;
  min-width: 36px;
  min-height: 36px;
}

.volume-icon-btn:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 2px;
}

.volume-icon-btn svg {
  width: 18px;
  height: 18px;
  fill: currentColor;
}

/* Range input styling */
.volume-slider {
  appearance: none;
  -webkit-appearance: none;
  width: 110px;
  height: 3px;
  background: rgba(255, 255, 255, 0.15);
  border-radius: 2px;
  outline: none;
  cursor: pointer;
}

.volume-slider::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-text-muted);
  cursor: pointer;
  transition: background var(--transition-fast), transform var(--transition-fast);
}

.volume-slider::-webkit-slider-thumb:hover {
  background: var(--color-text-main);
  transform: scale(1.2);
}

.volume-slider::-moz-range-thumb {
  width: 12px;
  height: 12px;
  border: none;
  border-radius: 50%;
  background: var(--color-text-muted);
  cursor: pointer;
  transition: background var(--transition-fast), transform var(--transition-fast);
}

.volume-slider::-moz-range-thumb:hover {
  background: var(--color-text-main);
  transform: scale(1.2);
}

.volume-slider:focus-visible {
  outline: 2px solid var(--color-focus);
  outline-offset: 4px;
}

/* --------------------------------------------------------------------------
   Notification / Error Banner
   -------------------------------------------------------------------------- */
.message-toast {
  position: fixed;
  bottom: 2rem;
  left: 50%;
  transform: translateX(-50%) translateY(20px);
  background: rgba(24, 26, 32, 0.95);
  border: 1px solid rgba(255, 255, 255, 0.12);
  color: var(--color-text-muted);
  font-size: 0.875rem;
  letter-spacing: 0.08em;
  padding: 0.75rem 1.75rem;
  border-radius: 9999px;
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.5s ease, transform 0.5s ease;
  z-index: 100;
  backdrop-filter: blur(8px);
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
}

.message-toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}

/* --------------------------------------------------------------------------
   Footer
   -------------------------------------------------------------------------- */
.app-footer {
  width: 100%;
  max-width: 800px;
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 2;
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  color: var(--color-text-dim);
  padding: 1rem 0;
}

/* --------------------------------------------------------------------------
   Accessibility: Reduced Motion
   -------------------------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  
  .ambient-glow {
    animation: none;
    opacity: 0.6;
  }

  .playing .enso-svg {
    animation: none;
  }
}

/* --------------------------------------------------------------------------
   Responsive Design
   -------------------------------------------------------------------------- */
@media (max-width: 480px) {
  .app-title {
    font-size: 2.25rem;
  }

  .app-subtext {
    font-size: 0.95rem;
    margin-bottom: 2rem;
  }

  .enso-container {
    width: 105px;
    height: 105px;
    margin-bottom: 1.8rem;
  }

  .playing-message {
    font-size: 1.1rem;
    line-height: 1.8;
  }

  .primary-btn {
    padding: 0.85rem 2.2rem;
    font-size: 0.95rem;
  }

  .guidance-text {
    font-size: 0.875rem;
  }
}