/* ============================================================
   LEARN YOUR WAY — style.css
   Monochrome · Dark/Light · Mobile-first
   ============================================================ */

/* --- Tokens ------------------------------------------------- */
:root {
  --font-display: 'DM Serif Display', Georgia, serif;
  --font-body: 'Inter', system-ui, sans-serif;

  /* Dark (default) */
  --bg:           #0a0a0a;
  --surface:      #141414;
  --surface-2:    #1e1e1e;
  --border:       #2a2a2a;
  --text-primary: #f0f0f0;
  --text-secondary: #888888;
  --text-tertiary: #555555;
  --btn-primary-bg: #f0f0f0;
  --btn-primary-text: #0a0a0a;
  --btn-secondary-bg: transparent;
  --btn-secondary-text: #f0f0f0;
  --btn-secondary-border: #3a3a3a;
  --tag-bg: #252525;
  --tag-text: #aaaaaa;
  --shadow: 0 1px 3px rgba(0,0,0,0.5);
}

[data-theme="light"] {
  --bg:           #f5f5f5;
  --surface:      #ffffff;
  --surface-2:    #f0f0f0;
  --border:       #e0e0e0;
  --text-primary: #111111;
  --text-secondary: #666666;
  --text-tertiary: #aaaaaa;
  --btn-primary-bg: #111111;
  --btn-primary-text: #ffffff;
  --btn-secondary-bg: transparent;
  --btn-secondary-text: #111111;
  --btn-secondary-border: #cccccc;
  --tag-bg: #ebebeb;
  --tag-text: #555555;
  --shadow: 0 1px 3px rgba(0,0,0,0.1);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text-primary);
  line-height: 1.6;
  transition: background 0.2s, color 0.2s;
  -webkit-font-smoothing: antialiased;
}

/* --- Container --------------------------------------------- */
.container {
  width: 100%;
  max-width: 720px;
  margin: 0 auto;
  padding: 0 20px;
}

/* --- Nav --------------------------------------------------- */
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 24px;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg);
}

.nav-logo {
  font-family: var(--font-display);
  font-size: 1.15rem;
  color: var(--text-primary);
  letter-spacing: -0.01em;
}

.theme-toggle {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: border-color 0.2s, color 0.2s;
}

.theme-toggle:hover {
  border-color: var(--text-secondary);
  color: var(--text-primary);
}

.theme-toggle:focus-visible {
  outline: 2px solid var(--text-primary);
  outline-offset: 2px;
}

/* --- Buttons ----------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 14px 28px;
  border-radius: 8px;
  font-family: var(--font-body);
  font-size: 0.95rem;
  font-weight: 500;
  text-decoration: none;
  border: 1px solid transparent;
  cursor: pointer;
  transition: opacity 0.15s, transform 0.1s;
  -webkit-tap-highlight-color: transparent;
  min-height: 48px;
}

.btn:active { transform: scale(0.98); }

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

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

.btn-primary:hover { opacity: 0.85; }

.btn-secondary {
  background: var(--btn-secondary-bg);
  color: var(--btn-secondary-text);
  border-color: var(--btn-secondary-border);
}

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

.btn-large {
  padding: 16px 40px;
  font-size: 1.05rem;
}

/* --- Hero -------------------------------------------------- */
.hero {
  padding: 80px 24px 72px;
  text-align: center;
}

.hero-inner {
  max-width: 600px;
  margin: 0 auto;
}

.hero-eyebrow {
  font-size: 0.78rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-tertiary);
  margin-bottom: 24px;
}

.hero-heading {
  font-family: var(--font-display);
  font-size: clamp(2.4rem, 8vw, 4rem);
  line-height: 1.15;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-bottom: 20px;
}

.hero-heading em {
  font-style: italic;
  color: var(--text-secondary);
}

.hero-sub {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 40px;
}

.hero-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* --- Problem strip ----------------------------------------- */
.problem {
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  padding: 40px 0;
  background: var(--surface);
}

.problem-text {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.8;
  text-align: center;
  max-width: 560px;
  margin: 0 auto;
}

.problem-text strong {
  color: var(--text-primary);
  font-weight: 600;
}

/* --- Section labels ---------------------------------------- */
.section-label {
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-tertiary);
  margin-bottom: 12px;
}

.section-heading {
  font-family: var(--font-display);
  font-size: clamp(1.6rem, 5vw, 2.4rem);
  line-height: 1.2;
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-bottom: 10px;
}

.section-sub {
  font-size: 1rem;
  color: var(--text-secondary);
  margin-bottom: 40px;
}

/* --- Demo section ------------------------------------------ */
.demo {
  padding: 72px 0;
}

.concept-source {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px 24px;
  margin-bottom: 28px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.concept-tag {
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-tertiary);
}

.concept-original {
  font-size: 0.95rem;
  color: var(--text-secondary);
  font-style: italic;
  line-height: 1.6;
}

/* --- Mode cards -------------------------------------------- */
.modes-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin-bottom: 40px;
}

@media (min-width: 600px) {
  .modes-grid { grid-template-columns: 1fr 1fr; }
}

.mode-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 20px;
  transition: border-color 0.2s;
}

.mode-card:hover {
  border-color: var(--text-tertiary);
}

.mode-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 14px;
}

.mode-icon {
  font-size: 1rem;
  color: var(--text-tertiary);
}

.mode-label {
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-secondary);
}

.mode-text {
  font-size: 0.92rem;
  color: var(--text-primary);
  line-height: 1.7;
}

.mode-text em {
  font-style: italic;
  color: var(--text-secondary);
}

/* Visual demo */
.visual-demo {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 6px;
}

.vd-box {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 8px 14px;
  font-size: 0.85rem;
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: 8px;
  width: 100%;
}

.vd-val {
  font-family: 'Courier New', monospace;
  font-size: 0.8rem;
  color: var(--text-primary);
  margin-left: auto;
}

.vd-addr { border-style: dashed; }
.vd-ptr { border-color: var(--text-tertiary); }

.vd-arrow {
  font-size: 0.78rem;
  color: var(--text-tertiary);
  padding-left: 14px;
}

/* Step list */
.steps-list {
  list-style: none;
  counter-reset: step-counter;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.steps-list li {
  counter-increment: step-counter;
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 0.88rem;
  color: var(--text-primary);
  line-height: 1.5;
}

.steps-list li::before {
  content: counter(step-counter);
  min-width: 22px;
  height: 22px;
  border: 1px solid var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--text-tertiary);
  flex-shrink: 0;
  margin-top: 1px;
}

/* Demo CTA */
.demo-cta {
  text-align: center;
  padding-top: 8px;
}

.demo-cta-text {
  font-size: 0.92rem;
  color: var(--text-secondary);
  margin-bottom: 20px;
}

/* --- How it works ------------------------------------------ */
.how {
  padding: 72px 0;
  border-top: 1px solid var(--border);
  background: var(--surface);
}

.steps-flow {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.flow-step {
  display: flex;
  gap: 20px;
  align-items: flex-start;
}

.flow-num {
  width: 40px;
  height: 40px;
  border: 1px solid var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text-secondary);
  flex-shrink: 0;
}

.flow-content h3 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 6px;
  padding-top: 8px;
}

.flow-content p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
}

.flow-divider {
  color: var(--text-tertiary);
  padding: 10px 0 10px 19px;
  font-size: 1rem;
}

/* --- Final CTA --------------------------------------------- */
.final-cta {
  padding: 80px 24px;
  text-align: center;
  border-top: 1px solid var(--border);
}

.final-heading {
  font-family: var(--font-display);
  font-size: clamp(1.8rem, 5vw, 2.8rem);
  letter-spacing: -0.02em;
  color: var(--text-primary);
  margin-bottom: 28px;
}

/* --- Footer ------------------------------------------------ */
.footer {
  padding: 28px 0;
  border-top: 1px solid var(--border);
  text-align: center;
}

.footer p {
  font-size: 0.8rem;
  color: var(--text-tertiary);
}

.footer-brand {
  color: var(--text-secondary);
}

/* --- Utility ----------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition: none !important;
    animation: none !important;
  }
}