:root {
  --bg: #f7f9fc;
  --surface: #ffffff;
  --surface-2: #eef3f8;
  --text: #132238;
  --muted: #637083;
  --line: #dce4ee;
  --brand: #1f6f5c;
  --brand-2: #164f43;
  --accent: #dff3eb;
  --navy: #0b1324;
  --shadow: 0 18px 50px rgba(17, 34, 56, .10);
  --radius: 18px;
  --max: 1180px;
}

html[data-theme="dark"] {
  --bg: #0d1420;
  --surface: #121d2c;
  --surface-2: #182638;
  --text: #edf4fb;
  --muted: #aab8c8;
  --line: #26384b;
  --accent: #173c34;
  --shadow: 0 18px 50px rgba(0, 0, 0, .28);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.55;
}
a { color: inherit; text-decoration: none; }
button, input, textarea, select { font: inherit; }
button { cursor: pointer; }
.section-shell { width: min(var(--max), calc(100% - 36px)); margin-inline: auto; }
.section-pad { padding-block: 84px; }
.skip { position: fixed; left: 12px; top: -60px; background: var(--surface); padding: 10px 14px; z-index: 999; border-radius: 8px; box-shadow: var(--shadow); }
.skip:focus { top: 12px; }

.site-header { position: sticky; top: 0; z-index: 100; background: color-mix(in srgb, var(--bg) 86%, transparent); backdrop-filter: blur(15px); border-bottom: 1px solid color-mix(in srgb, var(--line) 80%, transparent); }
.nav-wrap { width: min(var(--max), calc(100% - 36px)); height: 72px; margin: auto; display: flex; align-items: center; gap: 28px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-weight: 800; font-size: 1.2rem; letter-spacing: -.02em; }
.brand-mark { width: 35px; aspect-ratio: 1; display: grid; place-items: center; border-radius: 10px; color: white; background: linear-gradient(135deg, var(--brand), #3ba07f); box-shadow: 0 8px 20px rgba(31,111,92,.25); }
.main-nav { display: flex; gap: 22px; margin-left: auto; color: var(--muted); font-size: .95rem; font-weight: 600; }
.main-nav a:hover { color: var(--text); }
.nav-actions { display: flex; align-items: center; gap: 10px; }
.icon-btn { width: 40px; height: 40px; border-radius: 11px; border: 1px solid var(--line); background: var(--surface); color: var(--text); }
.mobile-menu { display: none; margin-left: auto; background: transparent; border: 0; color: var(--text); font-size: 1.35rem; }

.btn { border: 1px solid transparent; border-radius: 12px; min-height: 44px; padding: 10px 16px; display: inline-flex; align-items: center; justify-content: center; font-weight: 750; transition: transform .15s ease, border-color .15s ease, background .15s ease; }
.btn:hover { transform: translateY(-1px); }
.btn-small { min-height: 38px; padding: 8px 13px; font-size: .9rem; }
.btn-primary { background: var(--brand); color: white; }
.btn-primary:hover { background: var(--brand-2); }
.btn-ghost { background: var(--surface); border-color: var(--line); color: var(--text); }
.btn-ghost-invert { background: transparent; border-color: #50637a; color: #e8eef6; }
.full { width: 100%; }
.centered { margin: 28px auto 0; display: flex; }
.text-btn { border: 0; background: transparent; color: var(--brand); font-weight: 700; padding: 4px; }

.hero { min-height: 650px; display: grid; grid-template-columns: 1.15fr .85fr; gap: 70px; align-items: center; padding-block: 86px 64px; }
.eyebrow { margin: 0 0 10px; color: var(--brand); font-size: .76rem; letter-spacing: .14em; font-weight: 850; }
h1, h2, h3 { line-height: 1.12; margin-top: 0; letter-spacing: -.035em; }
h1 { font-size: clamp(2.7rem, 6vw, 5.5rem); margin-bottom: 24px; max-width: 10ch; }
h2 { font-size: clamp(2rem, 3.5vw, 3.2rem); margin-bottom: 12px; }
h3 { font-size: 1.2rem; }
.hero-lead { max-width: 670px; color: var(--muted); font-size: 1.12rem; }
.hero-actions, .button-row { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; }
.hero-points { display: flex; flex-wrap: wrap; gap: 18px; margin-top: 26px; color: var(--muted); font-size: .88rem; }
.hero-panel { background: var(--navy); color: #eaf0f7; border-radius: 26px; padding: 24px; box-shadow: 0 30px 70px rgba(8,17,31,.24); transform: rotate(1deg); }
.panel-topline { display: flex; justify-content: space-between; font-size: .82rem; color: #9fb0c5; margin-bottom: 18px; }
.focus-card { display: flex; align-items: center; justify-content: space-between; background: #131f32; border: 1px solid #25354d; border-radius: 17px; padding: 18px; }
.focus-card strong { font-size: 2rem; letter-spacing: -.04em; }
.micro { font-size: .7rem; margin: 0 0 2px; letter-spacing: .14em; color: #9fb0c5; }
.mini-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 12px; }
.mini-card { padding: 16px; background: #111b2c; border: 1px solid #23334b; border-radius: 15px; display: grid; gap: 3px; transition: background .15s ease, transform .15s ease; }
.mini-card:hover { background: #19263a; transform: translateY(-2px); }
.mini-card > span { color: #79c9ad; font-size: 1.3rem; }
.mini-card small { color: #91a2b6; }

.search-section { position: relative; margin-bottom: 18px; }
.search-box { display: grid; grid-template-columns: auto 1fr auto; gap: 12px; align-items: center; background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 0 16px; box-shadow: var(--shadow); }
.search-box input { border: 0; outline: 0; padding: 17px 0; background: transparent; color: var(--text); width: 100%; }
kbd { border: 1px solid var(--line); border-bottom-width: 2px; border-radius: 6px; padding: 2px 7px; color: var(--muted); background: var(--surface-2); font-size: .75rem; }
.search-results { position: absolute; top: calc(100% + 8px); left: 0; right: 0; z-index: 30; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; box-shadow: var(--shadow); padding: 10px; max-height: 360px; overflow: auto; }
.search-result { display: block; width: 100%; text-align: left; border: 0; background: transparent; color: var(--text); border-radius: 10px; padding: 12px; }
.search-result:hover { background: var(--surface-2); }
.search-result small { color: var(--muted); display: block; }

.section-heading { display: flex; align-items: end; justify-content: space-between; gap: 30px; margin-bottom: 30px; }
.section-heading p:not(.eyebrow) { color: var(--muted); max-width: 700px; margin-bottom: 0; }
.chip-row { display: flex; flex-wrap: wrap; gap: 8px; justify-content: end; }
.chip { border: 1px solid var(--line); background: var(--surface); color: var(--muted); border-radius: 99px; padding: 7px 12px; font-weight: 700; font-size: .85rem; }
.chip.active { background: var(--text); border-color: var(--text); color: var(--bg); }
.resource-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.lesson-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; min-height: 215px; display: flex; flex-direction: column; box-shadow: 0 8px 30px rgba(17,34,56,.04); }
.lesson-card .tag { display: inline-flex; align-self: flex-start; border-radius: 999px; background: var(--accent); color: var(--brand); padding: 5px 9px; font-size: .72rem; font-weight: 850; margin-bottom: 20px; }
.lesson-card h3 { margin-bottom: 8px; }
.lesson-card p { color: var(--muted); font-size: .92rem; }
.lesson-card button { margin-top: auto; align-self: flex-start; }

.tools-band { background: var(--navy); color: #eef3fa; }
.light-heading p:not(.eyebrow) { color: #9fb0c5; }
.tool-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; align-items: stretch; }
.tool-card { background: #111d2e; border: 1px solid #263852; border-radius: var(--radius); padding: 20px; }
.tool-card p { color: #9fb0c5; }
.tool-icon { width: 42px; height: 42px; display: grid; place-items: center; border-radius: 12px; background: #1b3044; color: #85d2b7; margin-bottom: 17px; font-weight: 850; }
.tool-card label { display: grid; gap: 5px; color: #b7c5d5; font-size: .8rem; margin-top: 10px; }
.tool-card input, .tool-card textarea { width: 100%; border: 1px solid #31455f; border-radius: 10px; background: #0c1626; color: white; padding: 10px 11px; outline: none; }
.timer-display { font-size: 2.4rem; font-weight: 850; letter-spacing: -.05em; margin: 22px 0 8px; }
.tool-output { display: block; min-height: 52px; background: #0c1626; border: 1px solid #31455f; border-radius: 10px; margin-top: 10px; padding: 12px; color: #c9d5e3; }
.save-status { margin-top: 8px; color: #7ea18f; font-size: .76rem; }
.flashcard { width: 100%; min-height: 120px; margin-top: 12px; border-radius: 13px; padding: 14px; background: #e8f5ef; color: #163d34; border: 0; display: grid; place-items: center; gap: 4px; font-weight: 800; }
.flashcard small { font-weight: 600; opacity: .6; }

.shortcut-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
.shortcut { background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 18px; transition: transform .15s ease, box-shadow .15s ease; }
.shortcut:hover { transform: translateY(-2px); box-shadow: var(--shadow); }
.shortcut .shortcut-icon { width: 38px; height: 38px; display: grid; place-items: center; border-radius: 10px; background: var(--surface-2); margin-bottom: 18px; font-weight: 850; }
.shortcut p { color: var(--muted); font-size: .84rem; margin-bottom: 0; }

.split-section { display: grid; grid-template-columns: 1.25fr .75fr; gap: 28px; align-items: start; }
.quiz-box, .formula-card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 22px; }
.quiz-top { display: flex; justify-content: space-between; gap: 10px; margin-bottom: 22px; }
.quiz-top select { border: 1px solid var(--line); border-radius: 10px; background: var(--surface); color: var(--text); padding: 9px 11px; }
.quiz-answers { display: grid; gap: 9px; }
.quiz-answer { text-align: left; border: 1px solid var(--line); background: var(--surface); color: var(--text); border-radius: 10px; padding: 12px; }
.quiz-answer:hover { border-color: var(--brand); }
.quiz-feedback { min-height: 24px; font-weight: 700; color: var(--brand); }
.formula-card dl { margin-bottom: 0; }
.formula-card dl div { padding: 13px 0; border-bottom: 1px solid var(--line); }
.formula-card dl div:last-child { border-bottom: 0; }
.formula-card dt { color: var(--muted); font-size: .78rem; }
.formula-card dd { margin: 3px 0 0; font-weight: 750; }

.planner-band { background: linear-gradient(135deg, #edf7f3, #eef4fb); color: #132238; }
html[data-theme="dark"] .planner-band { background: linear-gradient(135deg, #12241f, #142131); color: var(--text); }
.planner-layout { display: grid; grid-template-columns: .9fr 1.1fr; gap: 40px; }
.task-form { display: grid; gap: 10px; }
.task-form input, .task-form select { border: 1px solid var(--line); border-radius: 11px; background: var(--surface); color: var(--text); padding: 12px; }
.task-panel { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px; min-height: 270px; box-shadow: var(--shadow); }
.task-panel-head { display: flex; justify-content: space-between; margin-bottom: 12px; }
.task-list { display: grid; gap: 8px; }
.task-item { display: grid; grid-template-columns: auto 1fr auto; gap: 11px; align-items: center; padding: 12px; background: var(--surface-2); border-radius: 12px; }
.task-item.done .task-title { text-decoration: line-through; opacity: .55; }
.task-meta { display: block; color: var(--muted); font-size: .75rem; }
.priority-high { color: #b74343; font-weight: 800; }
.delete-task { background: transparent; border: 0; color: var(--muted); }
.empty { color: var(--muted); text-align: center; padding: 36px 10px; }

.newsletter { display: flex; align-items: center; justify-content: space-between; gap: 20px; }
.newsletter p:not(.eyebrow) { color: var(--muted); max-width: 760px; }
.site-footer { background: #09111e; color: #dce5f0; padding-top: 52px; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 30px; padding-bottom: 38px; }
.footer-grid > div { display: grid; align-content: start; gap: 8px; }
.footer-grid a:not(.brand) { color: #93a4b8; }
.footer-grid p { color: #93a4b8; }
.footer-bottom { border-top: 1px solid #1e2b3d; padding: 18px 0 30px; color: #7f91a6; font-size: .85rem; }
.footer-brand { margin-bottom: 6px; }

#lessonDialog { width: min(760px, calc(100% - 28px)); max-height: min(80vh, 760px); border: 1px solid var(--line); border-radius: 20px; padding: 0; background: var(--surface); color: var(--text); box-shadow: 0 30px 100px rgba(0,0,0,.3); }
#lessonDialog::backdrop { background: rgba(5,12,23,.55); backdrop-filter: blur(5px); }
.dialog-head { position: sticky; top: 0; display: flex; justify-content: space-between; align-items: start; gap: 20px; background: var(--surface); padding: 22px; border-bottom: 1px solid var(--line); }
.dialog-head h2 { font-size: 2rem; margin-bottom: 0; }
.dialog-content { padding: 24px; }
.dialog-content h3 { margin-top: 26px; }
.dialog-content ul { padding-left: 20px; }
.dialog-content .example { background: var(--surface-2); border-radius: 12px; padding: 14px; border-left: 3px solid var(--brand); }

@media (max-width: 1000px) {
  .hero { grid-template-columns: 1fr; gap: 35px; }
  h1 { max-width: 13ch; }
  .hero-panel { transform: none; }
  .resource-grid { grid-template-columns: repeat(2, 1fr); }
  .tool-grid, .shortcut-grid { grid-template-columns: repeat(2, 1fr); }
  .split-section, .planner-layout { grid-template-columns: 1fr; }
}

@media (max-width: 760px) {
  .main-nav, .nav-actions { display: none; }
  .mobile-menu { display: block; }
  .site-header.open .main-nav { position: absolute; display: grid; top: 72px; left: 18px; right: 18px; background: var(--surface); border: 1px solid var(--line); border-radius: 14px; padding: 14px; box-shadow: var(--shadow); }
  .hero { padding-top: 55px; min-height: auto; }
  h1 { font-size: clamp(2.7rem, 14vw, 4.6rem); }
  .section-pad { padding-block: 62px; }
  .section-heading { display: block; }
  .chip-row { justify-content: start; margin-top: 20px; }
  .resource-grid, .tool-grid, .shortcut-grid { grid-template-columns: 1fr; }
  .mini-grid { grid-template-columns: 1fr 1fr; }
  .search-box kbd { display: none; }
  .newsletter { align-items: flex-start; flex-direction: column; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
  .footer-grid > div:first-child { grid-column: 1 / -1; }
}

@media (max-width: 480px) {
  .section-shell { width: min(var(--max), calc(100% - 24px)); }
  .mini-grid { grid-template-columns: 1fr; }
  .hero-points { display: grid; gap: 8px; }
  .quiz-top { align-items: stretch; flex-direction: column; }
  .footer-grid { grid-template-columns: 1fr; }
  .footer-grid > div:first-child { grid-column: auto; }
}