:root {
  --ink: #171a18;
  --paper: #f4f1e9;
  --paper-deep: #eae6da;
  --green: #164d3a;
  --green-bright: #2e795c;
  --rust: #c35b38;
  --line: rgba(23, 26, 24, 0.16);
  --mono: "SFMono-Regular", "Cascadia Code", "Roboto Mono", monospace;
  --serif: "Iowan Old Style", "Palatino Linotype", "Yu Mincho", serif;
  --sans: Inter, "Helvetica Neue", "Hiragino Sans", sans-serif;
}

* { box-sizing: border-box; }

html { background: var(--paper); color: var(--ink); }

body {
  margin: 0;
  font-family: var(--sans);
  background:
    linear-gradient(rgba(23,26,24,.027) 1px, transparent 1px),
    linear-gradient(90deg, rgba(23,26,24,.027) 1px, transparent 1px),
    var(--paper);
  background-size: 26px 26px;
}

.shell { min-height: 100vh; }

.topbar {
  min-height: 84px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 14px clamp(24px, 5vw, 76px);
  border-bottom: 1px solid var(--line);
}

.brand {
  display: flex;
  gap: 14px;
  align-items: center;
  color: inherit;
  text-decoration: none;
}

.brand-logo-frame {
  display: grid;
  place-items: center;
  width: 132px;
  height: 50px;
  padding: 7px 11px;
  border-radius: 8px;
  border: 1px solid var(--line);
  background: #fff;
}

.brand-logo {
  display: block;
  width: 100%;
  height: 100%;
  object-fit: contain;
}

.brand small {
  display: block;
  color: #6c716c;
  font: 10px var(--mono);
  letter-spacing: .12em;
  text-transform: uppercase;
  margin-top: 2px;
}

.topbar-link {
  color: var(--green);
  text-decoration: none;
  font: 11px var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
}

.topbar-link span {
  margin-left: 6px;
  color: var(--rust);
  font-size: 16px;
}

.topbar-nav {
  display: flex;
  align-items: center;
  gap: 22px;
}

.topbar-link:hover { color: var(--rust); }

.kernel-status {
  font: 11px var(--mono);
  text-transform: uppercase;
  letter-spacing: .08em;
  display: flex;
  gap: 9px;
  align-items: center;
}

.status-dot {
  width: 8px;
  height: 8px;
  background: #3a9c72;
  border-radius: 50%;
  box-shadow: 0 0 0 4px rgba(58,156,114,.12);
}

main { padding: 0 clamp(24px, 5vw, 76px); }

.hero {
  min-height: 390px;
  display: grid;
  grid-template-columns: 1.25fr .75fr;
  align-items: center;
  border-bottom: 1px solid var(--line);
  position: relative;
  overflow: hidden;
}

.eyebrow {
  font: 11px var(--mono);
  color: var(--rust);
  letter-spacing: .15em;
  margin: 0 0 18px;
}

h1 {
  font: 400 clamp(48px, 6vw, 82px)/.98 var(--serif);
  letter-spacing: -.045em;
  margin: 0;
}

h1 em { color: var(--green); font-weight: 400; }

.hero-logo-heading { margin: 0; }

.hero-logo {
  display: block;
  width: min(100%, 520px);
  height: auto;
}

.lead {
  max-width: 580px;
  color: #5f655f;
  line-height: 1.8;
  margin: 26px 0 0;
}

.hero-symbol {
  justify-self: end;
  font: italic 130px/1 var(--serif);
  color: rgba(22,77,58,.10);
  transform: rotate(-8deg);
  user-select: none;
}

.tutorial-section {
  padding: 78px 0 0;
}

.tutorial-heading {
  margin-bottom: 28px;
}

.tutorial-heading .eyebrow {
  margin-bottom: 12px;
}

.tutorial-heading h1 {
  margin: 0;
  color: var(--ink);
  font: bold clamp(34px, 4vw, 52px) var(--sans);
  letter-spacing: -.035em;
}

.tutorial-lesson-select {
  display: grid;
  gap: 8px;
}

.tutorial-lesson-select label {
  color: #737a74;
  font: 9px var(--mono);
  letter-spacing: .12em;
  text-transform: uppercase;
}

.tutorial-lesson-select select {
  min-width: 190px;
}

.tutorial-heading > p {
  max-width: 430px;
  margin: 0;
  color: #656a66;
  font-size: 13px;
  line-height: 1.7;
}

.tutorial-shell {
  display: grid;
  grid-template-columns: minmax(220px, .72fr) minmax(330px, 1fr) minmax(330px, 1.12fr);
  height: min(720px, calc(100vh - 260px));
  min-height: 560px;
  border: 1px solid var(--ink);
  background: #faf8f2;
  box-shadow: 14px 14px 0 var(--paper-deep);
  overflow: hidden;
}

.tutorial-explanation-panel {
  min-width: 0;
  min-height: 0;
  padding: 27px 24px 25px;
  border-right: 1px solid var(--ink);
  overflow-y: auto;
  scrollbar-width: thin;
}

.tutorial-explanation-panel h2 {
  margin: 0 0 22px;
  color: var(--green);
  font: 400 24px/1.15 var(--serif);
  overflow-wrap: anywhere;
}

.tutorial-explanation {
  color: #5f675f;
  font-size: 12px;
  line-height: 1.75;
}

.tutorial-explanation p {
  margin: 0 0 18px;
}

.tutorial-explanation ol {
  margin: 0 0 19px;
  padding-left: 20px;
}

.tutorial-explanation li {
  padding: 4px 0 4px 3px;
}

.tutorial-explanation code,
.tutorial-state-note code {
  color: var(--green);
  font: 11px var(--mono);
}

.tutorial-tip {
  padding: 12px 13px;
  border-left: 3px solid var(--rust);
  background: #f0eee5;
  color: #6a706a;
  font-size: 11px;
}

.tutorial-subheading {
  margin: 0 0 10px;
  color: var(--rust);
  font: 10px var(--mono);
  letter-spacing: .12em;
  text-transform: uppercase;
}

.tutorial-allowed {
  margin: 0 0 24px;
  padding: 0 0 18px;
  border-bottom: 1px solid var(--line);
}

.tutorial-allowed ul {
  display: flex;
  flex-wrap: wrap;
  gap: 7px;
  margin: 0;
  padding: 0;
  list-style: none;
}

.tutorial-allowed li {
  padding: 5px 7px;
  border: 1px solid var(--line);
  background: #fffdf7;
}

.tutorial-allowed li code {
  color: var(--green);
  font: 10px var(--mono);
}

.tutorial-progress-step {
  margin: 0;
  padding: 18px 0 0;
  border-top: 1px solid var(--line);
}

.tutorial-progress-step code {
  color: var(--green);
  font: 11px var(--mono);
}

.tutorial-progress-step p {
  margin: 0 0 18px;
  color: #5f675f;
  font-size: 12px;
  line-height: 1.75;
}

.tutorial-entry-panel {
  min-width: 0;
  min-height: 0;
  display: flex;
  flex-direction: column;
  padding: 27px 28px 25px;
  border-right: 1px solid var(--ink);
  overflow: hidden;
}

.tutorial-card-head,
.tutorial-history-head,
.tutorial-input-head,
.tutorial-state-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 14px;
}

.tutorial-card-head .syntax-title,
.tutorial-history-head .syntax-title {
  margin-bottom: 10px;
}

.tutorial-card-head h2,
.tutorial-card-head h3 {
  max-width: 490px;
  margin: 0;
  color: var(--green);
  font: 400 18px/1.4 var(--serif);
  overflow-wrap: anywhere;
}

.tutorial-step-count {
  flex: 0 0 auto;
  color: var(--rust);
  font: 9px var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
}

.tutorial-script {
  flex: 1 1 auto;
  min-height: 0;
  margin: 23px 0 27px;
  padding: 14px 0;
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: #1b211e;
  overflow-x: auto;
}

.tutorial-script-line {
  min-width: max-content;
  display: grid;
  grid-template-columns: 42px 1fr;
  gap: 13px;
  padding: 2px 17px 2px 0;
  font: 12px/1.7 var(--mono);
}

.tutorial-script-line > span {
  color: #69736e;
  text-align: right;
  user-select: none;
}

.tutorial-script-line code {
  color: #dce8df;
  white-space: pre;
}

.tutorial-script-command {
  background: rgba(240,164,126,.11);
  border-left: 2px solid #f0a47e;
}

.tutorial-script-command > span { color: #f0a47e; }

.tutorial-empty-script {
  margin: 0;
  padding: 15px 20px;
  color: #a3ada6;
  font: 11px/1.6 var(--mono);
}

.tutorial-input-head {
  margin-bottom: 9px;
}

.tutorial-input-head label {
  color: var(--ink);
  font: 600 12px var(--sans);
}

.tutorial-input-head span {
  color: #7b817c;
  font: 10px var(--mono);
}

.tutorial-input-row {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  border: 1px solid var(--ink);
  background: #fffdf7;
}

.tutorial-input-row input {
  min-width: 0;
  width: 100%;
  border: 0;
  outline: 0;
  padding: 13px 14px;
  color: var(--green);
  background: transparent;
  font: 12px var(--mono);
}

.tutorial-input-row input::placeholder { color: #a2a6a0; }
.tutorial-input-row input:focus { box-shadow: inset 0 0 0 2px rgba(46,121,92,.22); }

.tutorial-input-row button {
  min-width: 95px;
  border: 0;
  border-left: 1px solid var(--ink);
  background: var(--rust);
  color: white;
  padding: 0 13px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  font: 600 11px var(--sans);
  cursor: pointer;
}

.tutorial-input-row button:hover { background: #a94628; }
.tutorial-input-row button:disabled { opacity: .55; cursor: wait; }

.tutorial-message {
  min-height: 22px;
  margin-top: 10px;
  color: #737a74;
  font: 10px/1.5 var(--mono);
}

.tutorial-message.accepted { color: var(--green); }
.tutorial-message.error { color: var(--rust); }

.tutorial-actions {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
}

.tutorial-reset-button {
  border: 0;
  padding: 0;
  color: #727872;
  background: transparent;
  font: 10px var(--mono);
  cursor: pointer;
}

.tutorial-reset-button:hover { color: var(--rust); }
.tutorial-reset-button:disabled { opacity: .5; cursor: wait; }

.tutorial-next-button {
  border: 1px solid var(--green);
  padding: 8px 11px;
  color: var(--green);
  background: transparent;
  font: 10px var(--mono);
  cursor: pointer;
}

.tutorial-next-button:hover { color: white; background: var(--green); }
.tutorial-next-button:disabled { opacity: .5; cursor: wait; }

.tutorial-history-panel {
  min-width: 0;
  min-height: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

.tutorial-history-head {
  flex: 0 0 auto;
  min-height: 70px;
  padding: 0 25px;
  border-bottom: 1px solid var(--line);
}

.tutorial-history-head .syntax-title { margin: 0; }

.tutorial-history {
  flex: 1 1 auto;
  min-height: 0;
  padding: 17px 18px 21px;
  overflow-y: auto;
  overflow-x: hidden;
  scrollbar-width: thin;
}

.tutorial-state {
  position: relative;
  margin: 0 0 13px;
  padding: 15px 17px 17px;
  border: 1px solid var(--line);
  background: #f3f2eb;
  cursor: pointer;
  transition: border-color .16s, background .16s, box-shadow .16s;
}

.tutorial-state:hover {
  border-color: var(--green);
  box-shadow: 3px 3px 0 rgba(34, 91, 68, .12);
}

.tutorial-state:focus-visible {
  outline: 2px solid var(--rust);
  outline-offset: 2px;
}

.tutorial-state:last-child { margin-bottom: 0; }

.tutorial-state::before {
  content: "";
  position: absolute;
  top: 0;
  bottom: -14px;
  left: 12px;
  width: 1px;
  background: var(--line);
  z-index: 0;
}

.tutorial-state:last-child::before { bottom: 50%; }

.tutorial-state.current {
  border-color: var(--green);
  background: #edf1eb;
}

.tutorial-state > * { position: relative; z-index: 1; }

.tutorial-state-head {
  color: #727a73;
  font: 9px var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
}

.tutorial-state-head span:first-child { color: var(--green); }

.tutorial-state-command {
  display: inline-block;
  margin: 11px 0 13px;
  padding: 7px 9px;
  color: var(--rust);
  background: #fffdf7;
  font: 11px var(--mono);
  overflow-wrap: anywhere;
}

.tutorial-state-start { margin: 11px 0 13px; }

.tutorial-state-body {
  border-top: 1px solid var(--line);
  padding-top: 12px;
}

.tutorial-goal {
  padding: 0 0 13px;
}

.tutorial-goal + .tutorial-goal {
  border-top: 1px solid var(--line);
  padding-top: 13px;
}

.tutorial-goal-inactive {
  opacity: .42;
  filter: grayscale(1);
}

.tutorial-goal-label {
  display: block;
  margin-bottom: 8px;
  color: var(--rust);
  font: 9px var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
}

.tutorial-context {
  margin: 0 0 10px;
  padding: 0 0 9px 15px;
  border-bottom: 1px solid var(--line);
  list-style: none;
}

.tutorial-variables,
.goal-variables {
  margin: 0 0 9px;
  color: #5f6761;
  font: 10px/1.6 var(--mono);
  overflow-wrap: anywhere;
}

.tutorial-variables strong,
.goal-variables strong {
  color: var(--rust);
  font-weight: 500;
}

.tutorial-context li {
  color: #5f6761;
  font: 10px/1.6 var(--mono);
  overflow-wrap: anywhere;
}

.tutorial-context strong { color: var(--rust); font-weight: 500; }

.tutorial-no-context,
.tutorial-state-note,
.tutorial-state-error {
  margin: 0;
  color: #6e766f;
  font: 11px/1.6 var(--mono);
}

.tutorial-state-error { color: var(--rust); }

.tutorial-goal-target {
  display: block;
  color: var(--green);
  font: 12px/1.6 var(--mono);
  overflow-wrap: anywhere;
}

.tutorial-complete {
  color: var(--green);
  font: 600 12px var(--sans);
}

.workspace {
  display: grid;
  grid-template-columns: minmax(0, 1.7fr) minmax(330px, .8fr);
  margin: 114px 0 94px;
  position: relative;
  border: 1px solid var(--ink);
  background: #faf8f2;
  box-shadow: 14px 14px 0 var(--paper-deep);
}

.workspace::before {
  content: "Try now";
  position: absolute;
  left: 0;
  bottom: calc(100% + 14px);
  font: bold clamp(34px, 4vw, 52px) var(--sans);
}

html[lang="ja"] .workspace::before { content: "今すぐ試す"; }

.editor-panel { border-right: 1px solid var(--ink); min-width: 0; }

.panel-head {
  height: 78px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 0 24px;
  border-bottom: 1px solid var(--line);
}

.panel-head > div { display: flex; align-items: baseline; gap: 13px; }
.panel-head h2 { font: 600 16px var(--sans); margin: 0; }
select {
  max-width: 180px;
  border: 1px solid var(--line);
  background: var(--paper);
  padding: 9px 28px 9px 11px;
  font: 12px var(--sans);
  color: var(--ink);
}

.editor-wrap {
  min-height: 420px;
  display: grid;
  grid-template-columns: 54px 1fr;
  background: #1b211e;
  position: relative;
}

.line-numbers {
  grid-column: 1;
  padding: 23px 13px;
  color: #69736e;
  border-right: 1px solid #303a35;
  text-align: right;
  font: 14px/1.75 var(--mono);
  user-select: none;
  white-space: pre;
}

.line-numbers span {
  display: block;
  height: 1.75em;
  transition: color .16s, background .16s;
}

.line-numbers span.active {
  color: #f0a47e;
  background: rgba(240,164,126,.12);
}

.editor-marker {
  position: absolute;
  z-index: 0;
  top: 23px;
  left: 54px;
  right: 0;
  height: 24.5px;
  border-left: 2px solid rgba(240,164,126,.75);
  background: rgba(240,164,126,.08);
  pointer-events: none;
  opacity: 0;
  transition: top .16s, height .16s, opacity .16s;
}

textarea {
  grid-column: 2;
  position: relative;
  z-index: 1;
  width: 100%;
  min-height: 420px;
  resize: vertical;
  border: 0;
  outline: 0;
  padding: 23px 25px;
  color: #dce8df;
  caret-color: #f0a47e;
  background: transparent;
  font: 14px/1.75 var(--mono);
  tab-size: 2;
  white-space: pre;
  overflow-x: auto;
}

.editor-footer {
  height: 72px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-left: 24px;
  border-top: 1px solid var(--ink);
}

.editor-footer > span { color: #777c77; font: 11px var(--mono); }

.footer-actions {
  align-self: stretch;
  display: flex;
}

.editor-footer button {
  height: 100%;
  min-width: 190px;
  border: 0;
  border-left: 1px solid var(--ink);
  background: var(--rust);
  color: white;
  padding: 0 25px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font: 600 13px var(--sans);
  cursor: pointer;
  transition: background .16s, padding .16s;
}

.editor-footer button:hover { background: #a94628; padding-right: 20px; }
.editor-footer button:disabled { opacity: .65; cursor: wait; }
.editor-footer .secondary-button {
  min-width: 155px;
  background: var(--paper);
  color: var(--green);
}
.editor-footer .secondary-button:hover { background: #e4e9e1; }
.button-arrow { font-size: 20px; }

.result-panel { display: flex; flex-direction: column; min-width: 0; }

.result {
  min-height: 285px;
  padding: 37px 30px 28px;
  border-bottom: 1px solid var(--line);
  transition: background .2s;
}

.result-icon {
  width: 52px;
  height: 52px;
  display: grid;
  place-items: center;
  border: 1px solid var(--green);
  color: var(--green);
  border-radius: 50%;
  font: 24px var(--serif);
  margin-bottom: 25px;
}

.result-kicker {
  font: 10px var(--mono);
  color: var(--rust);
  letter-spacing: .14em;
}

.result h3 { font: 400 25px var(--serif); margin: 8px 0 11px; }
.result > p:last-child { color: #666d67; font-size: 13px; line-height: 1.7; margin: 0; }
.result.success { background: rgba(46,121,92,.08); }
.result.success .result-icon { color: white; border-color: var(--green); background: var(--green); }
.result.error { background: rgba(195,91,56,.08); }
.result.error .result-icon { color: white; border-color: var(--rust); background: var(--rust); }

.certificate {
  margin-top: 18px;
  border-top: 1px solid var(--line);
  padding-top: 14px;
}

.certificate summary {
  color: var(--green);
  cursor: pointer;
  font: 11px var(--mono);
}

.certificate ol {
  max-height: 240px;
  overflow: auto;
  margin: 12px 0 0;
  padding-left: 28px;
}

.certificate li {
  padding: 3px 0;
  color: #69706a;
  font: 10px/1.5 var(--mono);
}

.certificate code {
  color: inherit;
  overflow-wrap: anywhere;
}

.interactive-card {
  padding: 24px 30px 27px;
  border-bottom: 1px solid var(--line);
  background: #f7f5ee;
}

.interactive-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 12px;
}

.goal-count {
  color: var(--rust);
  font: 9px var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
}

.goal-view {
  min-height: 90px;
  margin: 14px 0;
  padding: 15px;
  border-left: 3px solid var(--green);
  background: #ecefe8;
}

.goal-view p {
  margin: 0;
  color: #69706a;
  font-size: 12px;
  line-height: 1.55;
}

.goal-target {
  display: block;
  color: var(--green);
  font: 13px/1.6 var(--mono);
  overflow-wrap: anywhere;
}

.goal-context {
  margin: 0 0 12px;
  padding: 0 0 10px;
  border-bottom: 1px solid var(--line);
  list-style: none;
}

.goal-context li {
  color: #5f6761;
  font: 11px/1.6 var(--mono);
  overflow-wrap: anywhere;
}

.goal-context strong { color: var(--rust); font-weight: 500; }

.step-navigation {
  min-height: 51px;
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: stretch;
  border: 1px solid var(--ink);
}

.step-navigation-button {
  min-width: 0;
  border: 0;
  background: var(--green);
  color: white;
  padding: 0 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 9px;
  font: 600 11px var(--sans);
  cursor: pointer;
  transition: background .16s, opacity .16s;
}

.step-navigation-button:first-child {
  border-right: 1px solid var(--ink);
}

.step-navigation-button:last-child {
  border-left: 1px solid var(--ink);
}

.step-navigation-button:hover { background: #235f48; }
.step-navigation-button:disabled { opacity: .35; cursor: default; }

.navigation-arrow {
  font-size: 19px;
  line-height: 1;
}

.step-indicator {
  min-width: 108px;
  padding: 0 10px;
  display: grid;
  place-items: center;
  color: var(--rust);
  background: #f7f5ee;
  font: 9px/1.4 var(--mono);
  letter-spacing: .06em;
  text-align: center;
  text-transform: uppercase;
}

.step-command {
  display: block;
  margin-top: 6px;
  color: #69706a;
  font: 10px/1.5 var(--mono);
  overflow-wrap: anywhere;
}

.syntax-card { padding: 24px 30px 30px; }
.syntax-title { font: 10px var(--mono); letter-spacing: .14em; margin: 0 0 16px; }
.syntax-grid {
  display: grid;
  grid-template-columns: 1fr 1.3fr;
  gap: 10px 15px;
  font-size: 11px;
  align-items: baseline;
}
.syntax-grid code { color: var(--green); font: 11px var(--mono); }
.syntax-grid span { color: #7b817c; }

.axioms-section {
  padding: 86px 0 100px;
  border-top: 1px solid var(--line);
}

.section-heading {
  display: flex;
  justify-content: space-between;
  align-items: end;
  gap: 30px;
  margin-bottom: 35px;
}
.section-heading h2 { font: bold clamp(34px, 4vw, 52px) var(--sans); margin: 0; }
.section-heading > p { max-width: 430px; color: #656a66; font-size: 13px; line-height: 1.7; }

.axiom-list {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-top: 1px solid var(--ink);
}

.axiom {
  padding: 25px 22px 27px;
  border-bottom: 1px solid var(--line);
  display: grid;
  grid-template-columns: 38px 1fr;
  gap: 7px 15px;
}
.axiom:nth-child(odd) { border-right: 1px solid var(--line); }
.axiom-index { grid-row: 1 / 4; font: 10px var(--mono); color: var(--rust); padding-top: 4px; }
.axiom h3 { margin: 0; font: 600 15px var(--sans); }
.axiom-formula {
  overflow-x: auto;
  color: var(--green);
  font: 12px/1.6 var(--mono);
  white-space: nowrap;
  margin: 5px 0;
  scrollbar-width: thin;
}
.axiom p { margin: 0; color: #727772; font-size: 12px; line-height: 1.55; }
.axiom-kind { color: var(--rust); font: 10px var(--mono); font-weight: 400; }

.loading { padding: 35px 0; color: #777; font-size: 13px; }

footer {
  min-height: 80px;
  border-top: 1px solid var(--line);
  padding: 0 clamp(24px, 5vw, 76px);
  display: flex;
  align-items: center;
  justify-content: space-between;
  color: #7b807b;
  font: 10px var(--mono);
  text-transform: uppercase;
  letter-spacing: .08em;
}

@media (max-width: 1100px) and (min-width: 901px) {
  .tutorial-shell {
    grid-template-columns: 1fr;
    height: auto;
    min-height: 0;
    overflow: visible;
  }
  .tutorial-explanation-panel {
    max-height: 330px;
    border-right: 0;
    border-bottom: 1px solid var(--ink);
  }
  .tutorial-entry-panel {
    min-height: 470px;
    border-right: 0;
    border-bottom: 1px solid var(--ink);
  }
  .tutorial-history-panel { min-height: 470px; }
}

@media (max-width: 900px) {
  .hero { grid-template-columns: 1fr; min-height: 360px; }
  .hero-symbol { display: none; }
  .tutorial-shell {
    grid-template-columns: 1fr;
    height: auto;
    min-height: 0;
    overflow: visible;
  }
  .tutorial-explanation-panel {
    max-height: 330px;
    border-right: 0;
    border-bottom: 1px solid var(--ink);
  }
  .tutorial-entry-panel {
    min-height: 470px;
    border-right: 0;
    border-bottom: 1px solid var(--ink);
  }
  .tutorial-history-panel { min-height: 470px; }
  .workspace { grid-template-columns: 1fr; }
  .editor-panel { border-right: 0; border-bottom: 1px solid var(--ink); }
}

@media (max-width: 620px) {
  .kernel-status { display: none; }
  .topbar { padding-left: 16px; padding-right: 16px; }
  .brand { gap: 10px; }
  .topbar-nav { gap: 12px; }
  .brand-logo-frame { width: 112px; height: 43px; padding: 6px 9px; }
  .brand small { font-size: 9px; letter-spacing: .08em; }
  main { padding: 0 16px; }
  .hero { min-height: 330px; }
  h1 { font-size: 46px; }
  .tutorial-section { padding-top: 62px; }
  .tutorial-heading { margin-bottom: 22px; }
  .tutorial-lesson-select { margin-top: 21px; }
  .tutorial-lesson-select select { width: 100%; }
  .tutorial-heading > p { margin-top: 17px; }
  .tutorial-explanation-panel { max-height: 290px; padding: 22px 17px 21px; }
  .tutorial-entry-panel { padding: 22px 17px 21px; }
  .tutorial-history-head { min-height: 62px; padding: 0 17px; }
  .tutorial-history { padding: 14px 12px 17px; }
  .tutorial-state { padding: 14px 13px 15px; }
  .workspace { margin: 114px 0 70px; box-shadow: 7px 7px 0 var(--paper-deep); }
  .panel-head { padding: 0 15px; }
  select { max-width: 145px; }
  .editor-wrap { grid-template-columns: 39px 1fr; }
  .editor-marker { left: 39px; top: 20px; }
  textarea { padding: 20px 14px; font-size: 12px; }
  .line-numbers { padding: 20px 8px; font-size: 12px; }
  .editor-footer > span { display: none; }
  .editor-footer { justify-content: flex-end; }
  .footer-actions { width: 100%; }
  .editor-footer button { min-width: 0; width: 50%; }
  .interactive-card { padding: 22px 18px; }
  .step-navigation-button { padding: 0 9px; }
  .section-heading { display: block; }
  .axiom-list { grid-template-columns: 1fr; }
  .axiom:nth-child(odd) { border-right: 0; }
  footer { padding: 20px 16px; display: block; line-height: 2; }
}