/* ─────────────────────────────────────────
   ENGLISH TENSES — MINIMAL STUDY SHEET
   ───────────────────────────────────────── */

/* 1. TOKENS */
:root {
  --bg: #0d0d0f;
  --bg-card: #141416;
  --bg-card-2: #1a1a1e;
  --border: #232329;
  --border-soft: #1d1d22;

  --text: #e8e8ec;
  --text-2: #8e8e9a;
  --text-3: #5a5a68;

  --accent: #7c6cfa;
  --accent-soft: rgba(124, 108, 250, 0.1);

  --pos: #34c47a;
  --pos-soft: rgba(52, 196, 122, 0.1);
  --neg: #f2706d;
  --neg-soft: rgba(242, 112, 109, 0.1);
  --que: #f5a623;
  --que-soft: rgba(245, 166, 35, 0.1);

  --subj: rgba(124, 108, 250, 0.18);

  --radius: 10px;
  --radius-sm: 6px;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --font-sans: 'Inter', system-ui, sans-serif;

  --max-w: 920px;
  --pad: clamp(1rem, 4vw, 2rem);
}

/* 2. RESET */
*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}
html {
  scroll-behavior: smooth;
  font-size: 16px;
}
body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  min-height: 100dvh;
}
a {
  color: inherit;
  text-decoration: none;
}
ul {
  list-style: none;
}

/* 3. LAYOUT */
.container {
  max-width: var(--max-w);
  margin-inline: auto;
  padding-inline: var(--pad);
}

/* 4. HEADER */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(13, 13, 15, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  padding-block: 1.25rem;
}

.header-inner {
  display: flex;
  align-items: center;
  gap: 0.875rem;
  margin-bottom: 0.875rem;
}

.site-tag {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.15em;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid rgba(124, 108, 250, 0.2);
  border-radius: 4px;
  padding: 0.25em 0.6em;
  text-transform: uppercase;
}

.site-title {
  font-size: clamp(1.1rem, 2.5vw, 1.35rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--text);
}

.site-subtitle {
  font-size: 0.8rem;
  color: var(--text-3);
  margin-left: auto;
  font-variant-numeric: tabular-nums;
}

/* TOC */
.toc {
  overflow-x: auto;
  scrollbar-width: none;
}
.toc::-webkit-scrollbar {
  display: none;
}

#toc-list {
  display: flex;
  gap: 0.3rem;
  padding-bottom: 2px;
  white-space: nowrap;
}

#toc-list a {
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--text-3);
  padding: 0.3em 0.75em;
  border-radius: 40px;
  border: 1px solid transparent;
  transition:
    color 0.15s,
    border-color 0.15s,
    background 0.15s;
}

#toc-list a:hover,
#toc-list a.active {
  color: var(--accent);
  border-color: rgba(124, 108, 250, 0.3);
  background: var(--accent-soft);
}

/* 5. MAIN */
.main-content {
  padding-block: 2.5rem 4rem;
}

/* 6. MEMORY CARD */
.memory-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 3rem;
}

.memory-grid {
  display: flex;
  gap: 0;
  flex-wrap: wrap;
}

.memory-group {
  flex: 1;
  min-width: 180px;
  padding: 0.5rem 1.25rem;
}
.memory-group:first-child {
  padding-left: 0;
}
.memory-group:last-child {
  padding-right: 0;
}

.memory-divider {
  width: 1px;
  background: var(--border);
  margin-block: 0.25rem;
  flex-shrink: 0;
}

.memory-label {
  display: block;
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 0.625rem;
}

.memory-items {
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.memory-items span {
  font-size: 0.815rem;
  color: var(--text-2);
}

.memory-items em {
  font-style: normal;
  color: var(--text);
  font-weight: 500;
}

/* 7. TIME GROUP */
.time-group {
  position: relative;
  margin-bottom: 1rem;
}

.time-label {
  font-size: 0.65rem;
  font-weight: 600;
  letter-spacing: 0.15em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 1rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}
.time-label::after {
  content: '';
  flex: 1;
  height: 1px;
  background: var(--border);
}

/* 8. TENSE CARD */
.tense-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
  margin-bottom: 1rem;
  transition: border-color 0.2s;
  content-visibility: auto;
  contain-intrinsic-size: auto none auto 320px;
}

.tense-card:hover {
  border-color: #2e2e38;
}

/* Card header */
.card-header {
  display: flex;
  align-items: flex-start;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.tense-number {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  color: var(--text-3);
  background: var(--bg-card-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.3em 0.6em;
  flex-shrink: 0;
  margin-top: 0.1em;
}

.tense-name {
  font-size: clamp(1rem, 2vw, 1.15rem);
  font-weight: 600;
  letter-spacing: -0.02em;
  color: var(--text);
  line-height: 1.3;
  margin-bottom: 0.25rem;
}

.tense-use {
  font-size: 0.8rem;
  color: var(--text-2);
  line-height: 1.4;
}

/* Formula row */
.formula-row {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 1.5rem;
}

.formula-block {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  background: var(--bg-card-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.45em 0.8em;
  flex: 1;
  min-width: 180px;
}

.formula-tag {
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--text-3);
  width: 1ch;
  flex-shrink: 0;
}

.formula-block code {
  font-family: var(--font-mono);
  font-size: 0.775rem;
  color: var(--accent);
  letter-spacing: 0.01em;
}

/* Subject rules */
.subject-rules {
  margin-bottom: 1.25rem;
}

.rules-label {
  font-size: 0.62rem;
  font-weight: 600;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 0.5rem;
}

.rules-grid {
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.rule-row {
  display: flex;
  align-items: baseline;
  gap: 0.6rem;
  background: var(--bg-card-2);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.875rem;
  flex-wrap: wrap;
}

.rule-subjects {
  font-size: 0.8rem;
  color: var(--text-2);
  line-height: 1.6;
  flex-shrink: 0;
}

.rule-arrow {
  color: var(--text-3);
  font-size: 0.75rem;
  flex-shrink: 0;
}

.rule-form {
  font-family: var(--font-mono);
  font-size: 0.755rem;
  color: var(--accent);
  letter-spacing: 0.01em;
}

.rule-note {
  font-family: var(--font-sans);
  font-size: 0.72rem;
  color: var(--text-3);
  font-style: italic;
  letter-spacing: 0;
}

/* Examples grid */
.examples-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1px;
  background: var(--border-soft);
  border-radius: var(--radius-sm);
  overflow: hidden;
  border: 1px solid var(--border-soft);
}

.example-col {
  background: var(--bg);
  padding: 1rem;
}

.col-tag {
  display: inline-block;
  font-size: 0.62rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  border-radius: 4px;
  padding: 0.2em 0.6em;
  margin-bottom: 0.75rem;
}

.col-tag.positive {
  color: var(--pos);
  background: var(--pos-soft);
}
.col-tag.negative {
  color: var(--neg);
  background: var(--neg-soft);
}
.col-tag.question {
  color: var(--que);
  background: var(--que-soft);
}

.example-list {
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
}

.example-list li {
  font-size: 0.82rem;
  color: var(--text-2);
  line-height: 1.5;
}

/* Subject highlight */
mark.subj {
  background: var(--subj);
  color: var(--accent);
  border-radius: 3px;
  padding: 0 2px;
  font-weight: 500;
}

/* 9. FOOTER */
.site-footer {
  border-top: 1px solid var(--border);
  padding-block: 1.5rem;
}

.site-footer .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}

.back-to-top {
  font-size: 0.78rem;
  color: var(--text-3);
  font-weight: 500;
  padding: 0.4em 0.85em;
  border: 1px solid var(--border);
  border-radius: 40px;
  transition:
    color 0.15s,
    border-color 0.15s;
}
.back-to-top:hover {
  color: var(--text);
  border-color: var(--text-3);
}

.footer-note {
  font-size: 0.75rem;
  color: var(--text-3);
}

/* 10. RESPONSIVE */
@media (max-width: 700px) {
  .examples-grid {
    grid-template-columns: 1fr;
  }

  .formula-row {
    flex-direction: column;
  }

  .formula-block {
    min-width: unset;
  }

  .memory-grid {
    flex-direction: column;
    gap: 1rem;
  }

  .memory-divider {
    width: 100%;
    height: 1px;
    margin-block: 0;
  }

  .memory-group {
    padding: 0;
  }

  .site-subtitle {
    display: none;
  }

  .tense-card {
    padding: 1.25rem;
  }
}

@media (max-width: 500px) {
  .card-header {
    flex-direction: column;
    gap: 0.5rem;
  }
  .tense-number {
    align-self: flex-start;
  }
}

/* 11. REDUCED MOTION */
@media (prefers-reduced-motion: reduce) {
  * {
    transition: none !important;
  }
  html {
    scroll-behavior: auto;
  }
}