:root {
  color-scheme: dark;
  --dn-font-sans: 'Inter', 'Segoe UI', system-ui, -apple-system, BlinkMacSystemFont, 'Helvetica Neue', sans-serif;
  --dn-text: #f4f7ff;
  --dn-text-strong: #ffffff;
  --dn-muted: #9fb1d7;
  --dn-muted-soft: #7d8cb5;
  --dn-border: rgba(148, 163, 184, 0.35);
  --dn-border-strong: rgba(148, 163, 184, 0.5);
  --dn-bg: #030817;
  --dn-surface: #10172b;
  --dn-surface-muted: #0b1224;
  --dn-primary: #7dd3fc;
  --dn-primary-strong: #38bdf8;
  --dn-primary-soft: rgba(125, 211, 252, 0.14);
  --dn-success: #4ade80;
  --dn-warning: #facc15;
  --dn-focus: rgba(125, 211, 252, 0.45);
  --dn-radius-xs: 6px;
  --dn-radius-sm: 10px;
  --dn-radius-md: 12px;
  --dn-radius-lg: 16px;
  --dn-shadow-card: 0 35px 60px rgba(2, 6, 23, 0.65);
  --dn-shadow-soft: 0 18px 35px rgba(2, 6, 23, 0.45);
  --dn-spacing-1: 4px;
  --dn-spacing-2: 8px;
  --dn-spacing-3: 12px;
  --dn-spacing-4: 16px;
  --dn-spacing-5: 24px;
  --dn-spacing-6: 32px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: var(--dn-font-sans);
  font-size: 16px;
  line-height: 1.55;
  color: var(--dn-text);
  background-color: var(--dn-bg);
  background-image:
    radial-gradient(circle at 20% 20%, rgba(56, 189, 248, 0.12), transparent 45%),
    radial-gradient(circle at 80% 0%, rgba(14, 165, 233, 0.15), transparent 40%),
    linear-gradient(180deg, #030817 0%, #020510 100%);
  min-height: 100vh;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

body.dark,
body.timer-paused,
body.challenge-mode {
  background-color: var(--dn-bg);
  color: var(--dn-text);
}

body.light {
  background: #ffffff;
  color: #0f172a;
}

h1,
h2,
h3,
h4 {
  margin: 0 0 var(--dn-spacing-3);
  font-family: var(--dn-font-sans);
  color: var(--dn-text-strong);
}

h1 {
  font-size: clamp(2.2rem, 3.2vw, 2.75rem);
  font-weight: 500;
  letter-spacing: -0.01em;
}

h2 {
  font-size: clamp(1.5rem, 2.6vw, 2rem);
  font-weight: 600;
}

h3 {
  font-size: clamp(1.15rem, 2vw, 1.45rem);
  font-weight: 600;
  color: var(--dn-text);
}

p,
label,
small,
span,
li {
  font-size: 1rem;
  color: var(--dn-text);
}

p.lede,
.lede {
  font-size: 1.15rem;
  color: var(--dn-muted);
}

.dn-muted,
.dn-subtle-text,
small {
  color: var(--dn-muted);
  font-size: 0.95rem;
}

a {
  color: var(--dn-primary);
}

a:focus-visible,
button:focus-visible,
[role="button"]:focus-visible,
input:focus-visible,
select:focus-visible,
textarea:focus-visible {
  outline: 3px solid var(--dn-focus);
  outline-offset: 2px;
}

.dn-shell {
  width: min(1100px, 94vw);
  margin: var(--dn-spacing-6) auto;
}

.dn-card {
  background: linear-gradient(135deg, rgba(16, 23, 43, 0.92), rgba(9, 13, 26, 0.92));
  border-radius: var(--dn-radius-lg);
  padding: var(--dn-spacing-5);
  border: 1px solid var(--dn-border);
  box-shadow: var(--dn-shadow-card);
  backdrop-filter: blur(18px);
}

.dn-card + .dn-card {
  margin-top: var(--dn-spacing-5);
}

.dn-card header,
.dn-card footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--dn-spacing-2);
}

.dn-section-title {
  font-weight: 600;
  font-size: 1rem;
  color: var(--dn-muted);
  margin-bottom: var(--dn-spacing-2);
  letter-spacing: 0.02em;
  text-transform: none;
}

.dn-divider {
  width: 100%;
  height: 1px;
  border: 0;
  background: var(--dn-border);
  margin: var(--dn-spacing-3) 0;
}

.dn-pill {
  display: inline-flex;
  align-items: center;
  gap: var(--dn-spacing-2);
  padding: var(--dn-spacing-2) var(--dn-spacing-3);
  border-radius: 999px;
  background: rgba(17, 25, 47, 0.9);
  color: var(--dn-text);
  border: 1px solid var(--dn-border);
  font-weight: 600;
  font-size: 0.95rem;
}

.dn-pill strong {
  font-size: 1rem;
}

.dn-inline-icon {
  width: 1.1em;
  height: 1.1em;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.dn-inline-icon svg {
  width: 100%;
  height: 100%;
  stroke: currentColor;
  stroke-width: 1.8;
  fill: none;
  stroke-linecap: round;
  stroke-linejoin: round;
}

.btn,
button.btn,
.dn-button,
button.dn-button,
a.dn-button {
  font-family: var(--dn-font-sans);
  font-weight: 600;
  border-radius: var(--dn-radius-md);
  padding: 0.75rem 1.4rem;
  border: 1px solid transparent;
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease, box-shadow 0.2s ease, border-color 0.2s ease;
  font-size: 1rem;
  line-height: 1.2;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--dn-spacing-2);
  text-decoration: none;
  background: rgba(20, 28, 52, 0.8);
  border-color: var(--dn-border);
  color: var(--dn-text);
}

.btn:hover,
button.btn:hover,
.dn-button:hover {
  box-shadow: var(--dn-shadow-soft);
  transform: translateY(-1px);
}

.btn:disabled,
button.btn:disabled,
.dn-button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

.btn.primary,
.btn.btn-primary,
.dn-button-primary {
  background: linear-gradient(135deg, var(--dn-primary), var(--dn-primary-strong));
  color: #020617;
  border-color: var(--dn-primary-strong);
  box-shadow: 0 20px 45px rgba(56, 189, 248, 0.35);
}

.btn.secondary,
.btn.btn-secondary,
.dn-button-secondary {
  background: rgba(12, 18, 36, 0.75);
  color: var(--dn-text);
  border-color: var(--dn-border-strong);
}

.btn.ghost,
.dn-button-text {
  background: transparent;
  border-color: transparent;
  color: var(--dn-primary);
  padding-left: 0;
  padding-right: 0;
}

.btn.ghost:hover,
.dn-button-text:hover {
  color: var(--dn-primary);
  text-decoration: underline;
}

.dn-button-link {
  background: none;
  border-color: transparent;
  color: var(--dn-primary);
  padding-left: 0;
  padding-right: 0;
  box-shadow: none;
}

.dn-button-link:hover {
  text-decoration: underline;
}

input,
select,
textarea {
  width: 100%;
  border-radius: var(--dn-radius-md);
  border: 1px solid var(--dn-border-strong);
  padding: 0.75rem 0.95rem;
  font-size: 1rem;
  font-family: var(--dn-font-sans);
  background: rgba(11, 18, 36, 0.9);
  color: var(--dn-text);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

input:focus,
select:focus,
textarea:focus {
  border-color: var(--dn-primary);
  box-shadow: 0 0 0 3px var(--dn-focus);
  outline: none;
}

input::placeholder,
textarea::placeholder {
  color: var(--dn-muted);
}

label {
  font-weight: 600;
  color: var(--dn-text-strong);
  display: block;
  margin-bottom: var(--dn-spacing-2);
}

fieldset {
  border: none;
  padding: 0;
  margin: 0;
}

.dn-fade {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 0.35s ease, transform 0.35s ease;
}

.dn-fade.is-visible,
.dn-fade.show,
.dn-fade[aria-hidden="false"],
.dn-fade:not([hidden]) {
  opacity: 1;
  transform: translateY(0);
}

.dn-fade-up {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.35s ease, transform 0.35s ease;
}

.dn-fade-up.is-visible,
.dn-fade-up:not([hidden]) {
  opacity: 1;
  transform: translateY(0);
}

[aria-live] {
  min-height: 1.25rem;
}

.dn-status {
  font-size: 0.95rem;
  color: var(--dn-muted);
}

.dn-status[data-state="warning"] {
  color: var(--dn-warning);
}

.dn-status[data-state="success"] {
  color: var(--dn-success);
}

.dn-loader {
  display: inline-flex;
  align-items: center;
  gap: var(--dn-spacing-2);
  color: var(--dn-muted);
}

.dn-loader::before {
  content: '';
  width: 0.85rem;
  height: 0.85rem;
  border-radius: 50%;
  border: 2px solid var(--dn-border-strong);
  border-top-color: var(--dn-primary);
  animation: dn-spin 1s linear infinite;
}

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

@media (prefers-reduced-motion: reduce) {
  * {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }

  .dn-fade {
    opacity: 1;
    transform: none;
  }
}