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

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

img,
svg {
  display: block;
  max-width: 100%;
}

button,
input {
  font: inherit;
  color: inherit;
}

a {
  color: inherit;
  text-decoration: none;
}

:root {
  --color-bg: #0f172a;          
  --color-surface: #1e293b;      
  --color-surface-alt: #273548;  
  --color-border: #334155;       

  --color-text-primary: #f1f5f9;
  --color-text-secondary: #94a3b8;
  --color-text-muted: #64748b;

  --color-accent: #2dd4bf;       
  --color-accent-hover: #22b8a5;
  --color-error: #f87171;
  --color-error-bg: rgba(248, 113, 113, 0.1);
  --color-success: #4ade80;

  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;

  --font-family-base: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.5rem;
  --font-size-2xl: 1.875rem;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --shadow-card: 0 20px 40px -12px rgba(0, 0, 0, 0.5);

  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
}

body {
  font-family: var(--font-family-base);
  font-size: var(--font-size-base);
  background-color: var(--color-bg);
  color: var(--color-text-primary);
  line-height: 1.5;
  min-height: 100vh;
}

h1, h2, h3 {
  font-weight: 600;
  line-height: 1.25;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-sm);
  padding: 12px var(--space-lg);
  border: none;
  border-radius: var(--radius-md);
  font-size: var(--font-size-base);
  font-weight: 600;
  cursor: pointer;
  transition: background-color var(--transition-fast), transform var(--transition-fast), opacity var(--transition-fast);
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.btn-primary {
  background-color: var(--color-accent);
  color: var(--color-bg);
}

.btn-primary:hover:not(:disabled) {
  background-color: var(--color-accent-hover);
}

.btn-primary:active:not(:disabled) {
  transform: scale(0.98);
}

.btn-full {
  width: 100%;
}

.btn-spinner {
  width: 16px;
  height: 16px;
  border: 2px solid rgba(15, 23, 42, 0.3);
  border-top-color: var(--color-bg);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

.form-input {
  width: 100%;
  padding: 12px var(--space-md);
  background-color: var(--color-surface-alt);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  color: var(--color-text-primary);
  font-size: var(--font-size-base);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-input::placeholder {
  color: var(--color-text-muted);
}

.form-input:focus {
  outline: none;
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px rgba(45, 212, 191, 0.15);
}

.form-input.input-invalid {
  border-color: var(--color-error);
}

.form-input.input-invalid:focus {
  box-shadow: 0 0 0 3px rgba(248, 113, 113, 0.15);
}

:root[data-theme="light"] {
  --color-bg: #f4f6f8;
  --color-surface: #ffffff;
  --color-surface-alt: #eef1f4;
  --color-border: #dde3e8;
  --color-text-primary: #17212b;
  --color-text-secondary: #52616f;
  --color-text-muted: #8a97a3;
  --color-accent: #0d9488;
  --color-accent-hover: #0f766e;
}

:root[data-theme="grey"] {
  --color-bg: #26282c;
  --color-surface: #303236;
  --color-surface-alt: #3a3c41;
  --color-border: #47494f;
  --color-text-primary: #eceef0;
  --color-text-secondary: #b3b6bb;
  --color-text-muted: #85888d;
  --color-accent: #2dd4bf;
  --color-accent-hover: #22b8a5;
}

.theme-toggle-wrap {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 2500;
}

.theme-toggle-btn {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: 1px solid var(--color-border);
  background-color: var(--color-accent);
  color: var(--color-bg);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 6px 20px rgba(45, 212, 191, 0.3);
  transition: transform 200ms ease;
}

.theme-toggle-btn:hover { transform: scale(1.08); }

.theme-menu {
  position: absolute;
  bottom: 58px;
  right: 0;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 12px;
  padding: 8px;
  display: flex;
  flex-direction: column;
  gap: 4px;
  min-width: 140px;
  box-shadow: 0 12px 32px rgba(0,0,0,0.3);
}

.theme-menu[hidden] { display: none; }

.theme-option {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 9px 12px;
  background: none;
  border: none;
  border-radius: 8px;
  color: var(--color-text-secondary);
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  text-align: left;
  transition: background-color 150ms ease, color 150ms ease;
}

.theme-option:hover { background-color: var(--color-surface-alt); color: var(--color-text-primary); }
.theme-option-active { color: var(--color-accent); background-color: rgba(45, 212, 191, 0.1); }

.btn-loading-ring {
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: conic-gradient(from 0deg, transparent, currentColor);
  -webkit-mask: radial-gradient(farthest-side, transparent calc(100% - 3px), #000 calc(100% - 2px));
  mask: radial-gradient(farthest-side, transparent calc(100% - 3px), #000 calc(100% - 2px));
  animation: btn-spin 700ms linear infinite;
  display: inline-block;
}

@keyframes btn-spin {
  to { transform: rotate(360deg); }
}

.btn-loading-icon {
  display: inline-flex;
  animation: btn-bounce 900ms ease-in-out infinite;
}

@keyframes btn-bounce {
  0%, 100% { transform: translateY(0); opacity: 1; }
  50% { transform: translateY(-3px); opacity: 0.6; }
}

.btn-loading-download {
  animation-name: btn-bounce-down;
}

@keyframes btn-bounce-down {
  0%, 100% { transform: translateY(0); opacity: 1; }
  50% { transform: translateY(3px); opacity: 0.6; }
}

.network-status-wrap {
  position: fixed;
  top: 16px;
  right: 16px;
  z-index: 2400;
  display: flex;
  gap: 8px;
}

.network-status-pill {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: 999px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  box-shadow: 0 4px 12px rgba(0,0,0,0.15);
}

.network-status-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}

.network-status-dot-good { background-color: var(--color-success); box-shadow: 0 0 6px var(--color-success); }
.network-status-dot-fair { background-color: #fbbf24; box-shadow: 0 0 6px #fbbf24; }
.network-status-dot-poor { background-color: var(--color-error); box-shadow: 0 0 6px var(--color-error); }

@media (max-width: 640px) {
  .network-status-wrap {
    top: auto;
    bottom: 90px;
    right: 16px;
    flex-direction: column;
  }
}

.page-loading-overlay {
  position: fixed;
  inset: 0;
  z-index: 5000;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 16px;
  background-color: rgba(15, 23, 42, 0.55);
  backdrop-filter: blur(4px);
  transition: opacity 400ms ease;
}

.page-loading-overlay.page-loading-fade-out {
  opacity: 0;
  pointer-events: none;
}

.page-loading-ring-outer {
  width: 52px;
  height: 52px;
  position: relative;
}

.page-loading-ring-outer::before,
.page-loading-ring-outer::after {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: 50%;
  border: 3px solid transparent;
}

.page-loading-ring-outer::before {
  border-top-color: var(--color-accent);
  border-right-color: var(--color-accent);
  animation: page-loading-spin 900ms linear infinite;
}

.page-loading-ring-outer::after {
  border-bottom-color: rgba(45, 212, 191, 0.35);
  animation: page-loading-spin 1400ms linear infinite reverse;
}

@keyframes page-loading-spin {
  to { transform: rotate(360deg); }
}

.page-loading-text {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--color-text-secondary);
  letter-spacing: 0.03em;
}

.tutorial-video-overlay {
  position: fixed;
  inset: 0;
  z-index: 4500;
  background-color: rgba(0, 0, 0, 0.8);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}

.tutorial-video-card {
  position: relative;
  width: 100%;
  max-width: 720px;
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.5);
}

.tutorial-video-title {
  font-size: var(--font-size-lg);
  color: var(--color-text-primary);
  margin-bottom: 16px;
  padding-right: 32px;
}

.tutorial-video-player {
  width: 100%;
  border-radius: var(--radius-md);
  background-color: #000;
  max-height: 60vh;
}

.tutorial-video-close {
  position: absolute;
  top: 20px;
  right: 20px;
  background: none;
  border: none;
  color: var(--color-text-muted);
  cursor: pointer;
  padding: 6px;
  border-radius: var(--radius-sm);
}

.tutorial-video-close:hover {
  color: var(--color-text-primary);
  background-color: var(--color-surface-alt);
}

.site-intro-overlay {
  position: fixed;
  inset: 0;
  z-index: 6000;
  overflow: hidden;
  transition: opacity 700ms ease;
}

.site-intro-overlay.site-intro-fade-out {
  opacity: 0;
  pointer-events: none;
}

.site-intro-bg {
  position: absolute;
  inset: 0;
  background-size: cover;
  background-position: center;
}

.site-intro-overlay.site-intro-no-image .site-intro-bg {
  background: linear-gradient(160deg, #0f2c28 0%, var(--color-bg) 60%, #0a1a17 100%);
}

.site-intro-gradient {
  position: absolute;
  inset: 0;
  background: linear-gradient(180deg, rgba(15,23,42,0.55) 0%, rgba(15,23,42,0.85) 100%);
}

.site-intro-text-wrap {
  position: relative;
  z-index: 2;
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 24px;
}

.site-intro-main {
  font-size: 4rem;
  font-weight: 900;
  color: #fff;
  letter-spacing: 0.02em;
  text-shadow: 0 6px 30px rgba(0,0,0,0.6);
  opacity: 0;
  transform: translateY(24px);
  animation: site-intro-in 900ms 300ms cubic-bezier(0.22, 1, 0.36, 1) forwards;
}

.site-intro-sub {
  margin-top: 8px;
  font-size: 1.3rem;
  font-weight: 600;
  color: rgba(255,255,255,0.85);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  opacity: 0;
  transform: translateY(16px);
  animation: site-intro-in 900ms 700ms cubic-bezier(0.22, 1, 0.36, 1) forwards;
}

@keyframes site-intro-in {
  to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 640px) {
  .site-intro-main { font-size: 2.6rem; }
  .site-intro-sub { font-size: 1rem; }
}