:root{color-scheme:light;--bg:#FAF7F1;--panel:#ffffff;--text:#292524;--muted:#78716c;--border:#EDE9DD;--accent:#b8211c;--code:#F1EEE4;--button-text:#FAF7F1;--font-body:"Plus Jakarta Sans", "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;}
:root[data-theme="dark"]{color-scheme:dark;--bg:#171615;--panel:#22201f;--text:#faf7f1;--muted:#bfb7b1;--border:#48403c;--accent:#f07f7b;--code:#302b29;--button-text:#171615;--font-body:"Plus Jakarta Sans", "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;}
@media(prefers-color-scheme:dark){:root:not([data-theme="light"]){color-scheme:dark;--bg:#171615;--panel:#22201f;--text:#faf7f1;--muted:#bfb7b1;--border:#48403c;--accent:#f07f7b;--code:#302b29;--button-text:#171615;--font-body:"Plus Jakarta Sans", "Noto Sans JP", "Hiragino Kaku Gothic ProN", "Yu Gothic", sans-serif;}}
@font-face {
  font-family: "Plus Jakarta Sans";
  font-style: normal;
  font-weight: 200 800;
  font-display: swap;
  src: url("/fonts/plus-jakarta-sans.ttf") format("truetype");
}

.site-brand {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  margin: 0;
  color: inherit;
  font-family: var(--font-body, var(--chakra-fonts-heading));
  font-size: 2.25rem;
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -0.05em;
  text-decoration: none;
}
.site-brand svg {
  width: 3rem;
  height: 3rem;
  flex-shrink: 0;
}
.site-brand-ruby {
  color: var(--accent, var(--chakra-colors-accent));
}
@media (max-width: 767px) {
  .site-brand {
    font-size: 1.5rem;
  }
  .site-brand svg {
    width: 2.25rem;
    height: 2.25rem;
  }
}

* {
  box-sizing: border-box;
}
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.75 var(--font-body);
}
header,
footer {
  max-width: 1600px;
  margin: auto;
  padding: 22px 32px;
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}
header {
  border-bottom: 1px solid var(--border);
}
main {
  max-width: 1600px;
  margin: auto;
  padding: 28px 32px 48px;
}
a {
  color: var(--accent);
  text-underline-offset: 3px;
}
a:focus-visible,
summary:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 4px;
}
h1,
h2,
h3 {
  line-height: 1.25;
  letter-spacing: -0.025em;
}
h1 {
  font-size: clamp(1.6rem, 2.2vw, 1.9rem);
  margin: 12px 0 20px;
}
h2 {
  font-size: 1.15rem;
}
h3 {
  font-size: 1.1rem;
}
.lead {
  font-size: 1.05rem;
  color: var(--muted);
}
.eyebrow,
.note,
.prerequisite {
  color: var(--muted);
  font-size: 0.9rem;
}
.eyebrow {
  font-weight: 600;
}
section {
  margin: 32px 0;
}
nav[aria-label="Course contents"] section {
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
  padding: 12px 24px;
}
li {
  padding: 6px 0;
}
li p {
  margin: 2px 0 8px;
  color: var(--muted);
  font-size: 0.95rem;
}
pre {
  padding: 20px;
  overflow: auto;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: var(--code);
  font-size: 0.9rem;
  line-height: 1.65;
}
code {
  font-family: ui-monospace, monospace;
}
.button {
  display: inline-block;
  background: var(--accent);
  color: var(--button-text);
  border-radius: 8px;
  padding: 10px 18px;
  text-decoration: none;
  font-weight: 600;
}
details {
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px 20px;
}
summary {
  cursor: pointer;
  font-weight: 600;
}
details p {
  margin-bottom: 0;
}
.lesson-navigation {
  border-top: 1px solid var(--border);
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  gap: 24px;
  flex-wrap: wrap;
}
.lesson-navigation div {
  flex: 1;
  min-width: 180px;
}
.lesson-navigation span {
  display: block;
  color: var(--muted);
  font-size: 0.85rem;
}
.table-scroll {
  overflow: auto;
}
table {
  border-collapse: collapse;
  width: 100%;
  font-size: 0.9rem;
}
caption {
  text-align: left;
  font-weight: 600;
  padding: 8px 0;
}
td,
th {
  text-align: left;
  vertical-align: top;
  padding: 12px;
  border-bottom: 1px solid var(--border);
}
footer {
  font-size: 0.9rem;
  border-top: 1px solid var(--border);
}
@media (max-width: 480px) {
  main {
    padding: 24px 18px;
  }
  header,
  footer {
    padding: 18px;
  }
  pre {
    padding: 14px;
  }
  nav[aria-label="Course contents"] section {
    padding: 8px 16px;
  }
}

.embedded-playground {
  margin: 24px 0;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: var(--panel);
}
.embedded-playground label {
  display: block;
  font-weight: 600;
  margin-bottom: 10px;
}
.embedded-playground textarea {
  display: block;
  width: 100%;
  resize: vertical;
  min-height: 180px;
  padding: 16px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--code);
  color: var(--text);
  font:
    15px/1.6 ui-monospace,
    monospace;
  tab-size: 2;
}
.embedded-playground textarea:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
.runner-controls {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  margin-top: 16px;
}
.runner-controls button {
  font: inherit;
  cursor: pointer;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 8px 16px;
}
.runner-controls button:not(.button) {
  background: var(--panel);
  color: var(--text);
}
.runner-controls button:disabled {
  opacity: 0.6;
  cursor: wait;
}
.lesson-output pre {
  min-height: 72px;
  max-height: 350px;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}
.runner-error {
  color: var(--accent);
  white-space: pre-wrap;
  overflow-wrap: anywhere;
}
.practice-task {
  border-left: 3px solid var(--accent);
  padding: 4px 20px;
  background: var(--code);
}
@media (max-width: 480px) {
  .embedded-playground {
    padding: 12px;
  }
  .embedded-playground textarea {
    padding: 10px;
  }
}

.lesson-version {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  margin-bottom: 16px;
}
.lesson-version label {
  margin: 0;
}
.lesson-version select {
  font: inherit;
  max-width: 100%;
  padding: 8px;
  background: var(--panel);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.version-navigation {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 24px;
}
.version-navigation a {
  padding: 6px 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 0.9rem;
}
.version-navigation a[aria-current="page"] {
  background: var(--accent);
  color: var(--bg);
  text-decoration: none;
  font-weight: 600;
}
.version-note {
  border-left: 3px solid var(--accent);
  padding: 12px 18px;
  background: var(--code);
}

header {
  align-items: center;
}
#tutorial-header-controls {
  margin-left: auto;
  max-width: 100%;
}
.tutorial-header-controls {
  display: flex;
  gap: 18px;
  align-items: center;
  flex-wrap: wrap;
  font-size: 0.85rem;
}
.header-version,
.header-theme {
  display: flex;
  gap: 8px;
  align-items: center;
  max-width: 100%;
  flex-wrap: wrap;
}
.header-version select {
  font: inherit;
  padding: 7px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--panel);
  color: var(--text);
  max-width: 100%;
}
.header-theme input {
  appearance: none;
  width: 40px;
  height: 24px;
  border-radius: 14px;
  border: 1px solid var(--border);
  background: var(--muted);
  position: relative;
  cursor: pointer;
  margin: 0;
}
.header-theme input::after {
  content: "";
  position: absolute;
  width: 18px;
  height: 18px;
  background: var(--panel);
  border-radius: 50%;
  top: 2px;
  left: 2px;
}
.header-theme input:checked {
  background: var(--accent);
}
.header-theme input:checked::after {
  left: 18px;
}
.header-theme input:focus-visible,
.header-version select:focus-visible {
  outline: 3px solid var(--accent);
  outline-offset: 3px;
}
@media (max-width: 700px) {
  #tutorial-header-controls {
    margin-left: 0;
    width: 100%;
  }
  .tutorial-header-controls {
    justify-content: space-between;
  }
}

/* Keep the lesson, experiment and course navigation in one workspace. */
header,
footer,
.breadcrumbs {
  max-width: 1600px;
  padding: 22px 32px;
}
header > a {
  text-decoration: none;
  font-weight: 650;
}
header > a:nth-child(2) {
  display: none;
}
.breadcrumbs {
  margin: auto;
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
  font-size: 0.85rem;
  border-bottom: 1px solid var(--border);
  padding-top: 0;
}
main {
  max-width: 1600px;
  padding: 28px 32px 48px;
}
h1 {
  font-size: clamp(1.6rem, 2.2vw, 1.9rem);
}
.lesson-layout {
  display: grid;
  grid-template-columns: 200px minmax(0, 1fr);
  gap: 28px;
}
.lesson-layout article {
  min-width: 0;
}
.course-sidebar {
  border-right: 1px solid var(--border);
  padding-right: 20px;
  align-self: start;
  position: sticky;
  top: 20px;
  max-height: calc(100vh - 40px);
  overflow-y: auto;
}
.course-sidebar details {
  border: 0;
  padding: 0;
}
.course-sidebar summary {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--muted);
}
.course-sidebar nav a {
  display: flex;
  align-items: baseline;
  gap: 10px;
  text-decoration: none;
  font-size: 0.8rem;
  line-height: 1.45;
  padding: 9px 8px;
  border-radius: 5px;
  color: var(--muted);
}
.course-sidebar nav a[aria-current="page"] {
  color: var(--accent);
  background: var(--code);
  font-weight: 650;
}
.lesson-number {
  color: var(--muted);
  font-variant-numeric: tabular-nums;
  flex-shrink: 0;
}
.lesson-workspace {
  display: grid;
  grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr);
  gap: 32px;
  align-items: start;
}
.lesson-explanation section:first-child {
  margin-top: 12px;
}
.lesson-editor {
  position: sticky;
  top: 20px;
  min-width: 0;
}
.embedded-playground {
  margin: 12px 0 24px;
  padding: 16px;
}
.embedded-playground textarea {
  min-height: 300px;
  font-size: 14px;
}
details {
  padding: 12px 14px;
  font-size: 0.85rem;
}
button.button {
  border: 0;
  font: inherit;
  cursor: pointer;
}
button[hidden] {
  display: none;
}
.course-home {
  max-width: 1000px;
  margin: 20px auto;
}
nav[aria-label="Course contents"] .course-chapter {
  border: 0;
  padding: 0;
  background: transparent;
}
.course-chapter h3 {
  font-size: 0.85rem;
  color: var(--muted);
}
.lesson-cards {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 14px;
}
.lesson-card {
  display: flex;
  gap: 16px;
  padding: 20px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--panel);
  text-decoration: none;
  color: var(--text);
}
.lesson-card:hover {
  border-color: var(--accent);
}
.lesson-card div {
  flex: 1;
}
.lesson-card p {
  font-size: 0.85rem;
  color: var(--muted);
  line-height: 1.6;
  margin: 6px 0 0;
}
@media (max-width: 1150px) {
  .lesson-workspace {
    grid-template-columns: minmax(0, 1fr);
    gap: 0;
  }
  .lesson-editor {
    position: static;
    grid-row: 1;
  }
}
@media (max-width: 760px) {
  header,
  footer,
  .breadcrumbs {
    padding-left: 18px;
    padding-right: 18px;
  }
  main {
    padding: 20px 18px 36px;
  }
  .lesson-layout {
    display: block;
  }
  .course-sidebar {
    position: static;
    max-height: none;
    border-right: 0;
    border-bottom: 1px solid var(--border);
    padding: 0 0 16px;
    margin-bottom: 24px;
  }
  .course-sidebar details[open] nav {
    max-height: 240px;
    overflow-y: auto;
  }
  .lesson-cards {
    grid-template-columns: minmax(0, 1fr);
  }
  .course-home {
    margin-top: 0;
  }
  .embedded-playground textarea {
    min-height: 220px;
  }
}

/* One editor surface, with all actions beside the Run control. */
.embedded-playground {
  padding: 0;
  overflow: hidden;
  border-radius: 7px;
}
.editor-heading {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 10px 16px;
  background: var(--code);
  border-bottom: 1px solid var(--border);
}
.editor-heading label {
  margin: 0;
  font-size: 0.8rem;
}
.editor-heading .note {
  font-size: 0.75rem;
}
.embedded-playground textarea {
  border: 0;
  border-radius: 0;
  background: var(--code);
  padding: 18px 16px;
}
.embedded-playground textarea:focus-visible {
  outline-offset: -2px;
}
.runner-controls {
  margin: 0;
  gap: 8px;
  padding: 12px;
  align-items: center;
  background: var(--code);
  border-top: 1px solid var(--border);
}
.runner-controls button {
  font-size: 0.8rem;
  padding: 8px 12px;
  border-radius: 6px;
}
.runner-controls a {
  margin-left: auto;
  font-size: 0.75rem;
  text-decoration: none;
}
.lesson-output {
  padding: 16px;
  border-top: 1px solid var(--border);
}
.lesson-output h3 {
  margin: 0 0 12px;
  font-size: 0.8rem;
  color: var(--muted);
}
.lesson-output pre {
  padding: 0;
  margin: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  min-height: 80px;
}
.runner-status,
.embedded-playground > [role="alert"] {
  padding: 0 16px;
  font-size: 0.8rem;
}
.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}
.lesson-explanation section {
  margin: 28px 0;
}
.lesson-explanation h2 {
  font-size: 1.05rem;
}
.lesson-explanation li {
  font-size: 0.85rem;
}
.eyebrow {
  font-size: 0.75rem;
  letter-spacing: 0.04em;
}
@media (max-width: 480px) {
  .embedded-playground {
    padding: 0;
  }
  .editor-heading {
    flex-wrap: wrap;
    gap: 4px 12px;
  }
  .runner-controls a {
    width: 100%;
    margin-top: 4px;
  }
}

.experiments {
  padding-left: 22px;
}
.experiments li {
  margin-bottom: 22px;
  padding-left: 4px;
}
.experiments h3 {
  font-size: 0.95rem;
  margin: 0 0 8px;
}
.experiments p {
  color: var(--text);
  font-size: 0.9rem;
  margin-bottom: 12px;
}

.course-sidebar nav .sidebar-chapter {
  border: 0;
  border-radius: 0;
  padding: 0;
  background: transparent;
  margin: 16px 0;
}
.sidebar-chapter h3 {
  margin: 0 8px 6px;
  font-size: 0.72rem;
  color: var(--muted);
  letter-spacing: 0.03em;
}

.example-code {
  padding: 0;
  border: 0;
  border-radius: 0;
  background: transparent;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  font-size: 0.82rem;
}
.sample-choice {
  padding: 8px 12px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--panel);
  color: var(--text);
  font: inherit;
  font-size: 0.82rem;
  cursor: pointer;
  text-align: left;
}
.sample-choice[aria-pressed="true"] {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--code);
}
.sample-choice:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}
.experiments {
  list-style: none;
  padding: 0;
}
.experiments li {
  padding: 12px;
  margin-bottom: 12px;
  border: 1px solid var(--border);
  border-radius: 7px;
}
.experiments p {
  margin: 10px 0 0;
  color: var(--muted);
}