:root {
  --ink: #14201d;
  --muted: #5e6d68;
  --paper: #f6f2e9;
  --paper-deep: #eee8dc;
  --surface: #fffdf8;
  --green: #153f34;
  --green-bright: #1f6a54;
  --mint: #c9edda;
  --orange: #e06c3c;
  --yellow: #f3c75f;
  --line: #d7d1c5;
  --code: #17211f;
  --white: #ffffff;
  --shadow: 0 18px 50px rgba(27, 51, 43, 0.1);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.55;
}

button, input, textarea { font: inherit; }

button { color: inherit; }

.skip-link {
  position: fixed;
  z-index: 100;
  top: 8px;
  left: 8px;
  padding: 10px 14px;
  color: var(--white);
  background: var(--green);
  border-radius: 6px;
  transform: translateY(-150%);
}

.skip-link:focus { transform: translateY(0); }

.site-header {
  position: sticky;
  z-index: 20;
  top: 0;
  display: flex;
  min-height: 76px;
  align-items: center;
  justify-content: space-between;
  padding: 12px clamp(20px, 4vw, 64px);
  color: var(--white);
  background: rgba(21, 63, 52, 0.97);
  border-bottom: 1px solid rgba(255, 255, 255, 0.12);
  backdrop-filter: blur(12px);
}

.brand {
  display: inline-flex;
  gap: 12px;
  align-items: center;
  color: inherit;
  text-decoration: none;
  line-height: 1.1;
}

.brand-mark {
  width: 42px;
  height: 42px;
  object-fit: cover;
  background: var(--white);
  border: 2px solid rgba(255, 255, 255, 0.9);
  border-radius: 50%;
}

.brand strong, .brand small { display: block; }
.brand strong { font-size: 1rem; letter-spacing: 0.01em; }
.brand small { margin-top: 4px; color: #b9d9cc; font-size: 0.72rem; letter-spacing: 0.12em; text-transform: uppercase; }

.header-meta { display: flex; gap: 18px; align-items: center; }
.quiet-button, .text-button {
  padding: 5px 2px;
  color: inherit;
  background: none;
  border: 0;
  border-bottom: 1px solid currentColor;
  cursor: pointer;
}
.quiet-button { color: #fff; font-size: 0.82rem; }

.tutorial-shell {
  display: grid;
  grid-template-columns: 250px minmax(0, 1fr);
  width: min(1460px, 100%);
  min-height: calc(100vh - 76px);
  margin: 0 auto;
}

.tutorial-nav {
  position: sticky;
  top: 76px;
  align-self: start;
  height: calc(100vh - 76px);
  padding: 48px 28px;
  border-right: 1px solid var(--line);
}

.eyebrow, .section-label {
  margin: 0 0 13px;
  color: var(--green-bright);
  font-size: 0.75rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}

.step-list { display: grid; gap: 6px; margin: 0; padding: 0; list-style: none; }
.step-button {
  display: flex;
  width: 100%;
  gap: 12px;
  align-items: center;
  padding: 9px 10px;
  color: var(--muted);
  background: transparent;
  border: 0;
  border-radius: 9px;
  font-size: 0.92rem;
  font-weight: 650;
  text-align: left;
  cursor: pointer;
}
.step-button:hover { color: var(--ink); background: rgba(255, 255, 255, 0.55); }
.step-button.is-active { color: var(--green); background: var(--surface); box-shadow: 0 5px 18px rgba(28, 48, 42, 0.07); }
.step-dot {
  display: grid;
  flex: 0 0 auto;
  width: 28px;
  height: 28px;
  place-items: center;
  border: 1px solid #bfc4be;
  border-radius: 50%;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.74rem;
}
.is-active .step-dot { color: var(--white); background: var(--green); border-color: var(--green); }
.is-complete .step-dot { color: var(--green); background: var(--mint); border-color: var(--mint); }

.progress-summary { margin-top: 42px; padding-top: 24px; border-top: 1px solid var(--line); }
.progress-label { display: flex; justify-content: space-between; color: var(--muted); font-size: 0.78rem; }
.progress-label strong { color: var(--green); }
.progress-track { height: 5px; margin: 10px 0 12px; overflow: hidden; background: #ddd8cc; border-radius: 5px; }
.progress-track span { display: block; width: 0; height: 100%; background: var(--orange); border-radius: inherit; transition: width 300ms ease; }
.progress-summary p { margin: 0; color: var(--muted); font-size: 0.74rem; }

.tutorial-main { min-width: 0; padding: clamp(34px, 6vw, 78px); outline: none; }
#screen { width: min(1020px, 100%); margin: 0 auto; }

.welcome-card {
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(280px, 0.65fr);
  overflow: hidden;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 24px;
  box-shadow: var(--shadow);
}

.welcome-copy { padding: clamp(38px, 6vw, 78px); }
h1, h2, h3, p { text-wrap: pretty; }
h1, h2, h3 { line-height: 1.12; }
h1 { margin: 0; font-size: clamp(2.65rem, 6vw, 5.7rem); letter-spacing: -0.065em; }
h1 span { color: var(--orange); }
.lede { max-width: 720px; margin: 24px 0 28px; color: var(--muted); font-size: clamp(1.02rem, 1.8vw, 1.25rem); }

.code-editor:focus { border-color: var(--green-bright); box-shadow: 0 0 0 3px rgba(31, 106, 84, 0.15); }

.primary-button, .secondary-button {
  display: inline-flex;
  gap: 10px;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 11px 18px;
  border-radius: 8px;
  font-weight: 750;
  cursor: pointer;
}
.primary-button { color: var(--white); background: var(--green); border: 1px solid var(--green); }
.primary-button:hover { background: #0d3027; }
.welcome-copy > .primary-button { margin-top: 18px; }
.secondary-button { color: var(--green); background: transparent; border: 1px solid #9ca8a2; }
.secondary-button:hover { background: #eef2ed; }
.secondary-button:disabled { cursor: not-allowed; opacity: 0.45; }

.route-card { padding: clamp(34px, 5vw, 58px) clamp(28px, 4vw, 48px); color: var(--white); background: var(--green); }
.route-card .eyebrow { color: #9ed5bd; }
.route-card ol { margin: 35px 0; padding: 0; list-style: none; }
.route-card li { display: flex; gap: 16px; align-items: center; padding: 24px 0; border-bottom: 1px solid rgba(255,255,255,0.14); }
.route-card li > span { color: var(--yellow); font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: 0.77rem; }
.route-card strong { display: block; }
.route-footnote { color: #bcd4ca; font-size: 0.82rem; }

.lesson { display: grid; gap: 48px; }
.lesson-header { display: flex; justify-content: space-between; align-items: flex-start; padding-bottom: 38px; border-bottom: 1px solid var(--line); }
.lesson-header h1 { max-width: 760px; font-size: clamp(2.35rem, 5vw, 4.6rem); }
.lesson-number { color: #c7c0b4; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; font-size: clamp(2rem, 4vw, 3.7rem); font-weight: 300; }

.concept-grid { display: grid; grid-template-columns: minmax(0, 0.9fr) minmax(380px, 1.1fr); gap: clamp(28px, 5vw, 65px); align-items: center; }
.concept-copy h2 { margin: 0 0 24px; font-family: Georgia, "Times New Roman", serif; font-size: clamp(1.45rem, 2.4vw, 2.1rem); font-weight: 500; }
.concept-copy ul { margin: 0; padding: 0; list-style: none; }
.concept-copy li { position: relative; margin: 11px 0; padding-left: 23px; color: var(--muted); }
.concept-copy li::before { position: absolute; top: 0.62em; left: 0; width: 8px; height: 2px; content: ""; background: var(--orange); }

.code-card, .solution-panel pre {
  overflow-x: auto;
  margin: 0;
  padding: 28px;
  color: #eaf7f0;
  background: var(--code);
  border-radius: 14px;
  box-shadow: 10px 10px 0 var(--mint);
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.86rem;
  line-height: 1.75;
  white-space: pre-wrap;
}

/* Prism supplies the Java parser; these token colors keep it in our field-guide palette. */
.token.comment,
.token.prolog,
.token.doctype,
.token.cdata { color: #80968c; font-style: italic; }
.token.punctuation { color: #d6e1dc; }
.token.namespace { opacity: 0.8; }
.token.property,
.token.tag,
.token.constant,
.token.symbol,
.token.deleted { color: #ef8a62; }
.token.boolean,
.token.number { color: #d6a6f2; }
.token.selector,
.token.attr-name,
.token.string,
.token.char,
.token.builtin,
.token.inserted { color: #f3c75f; }
.token.operator,
.token.entity,
.token.url,
.language-css .token.string,
.style .token.string { color: #abdac5; }
.token.atrule,
.token.attr-value,
.token.keyword { color: #f08a5d; font-weight: 650; }
.token.function,
.token.class-name { color: #86c7ed; }
.token.regex,
.token.important,
.token.variable { color: #f0b95b; }
.token.annotation,
.token.annotation .token.punctuation { color: #9fe0c0; }
.token.important,
.token.bold { font-weight: 800; }
.token.italic { font-style: italic; }

.workbench, .questions {
  padding: clamp(24px, 4vw, 42px);
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 18px;
  box-shadow: 0 10px 28px rgba(41, 55, 49, 0.06);
}
.workbench-head { display: flex; gap: 24px; align-items: flex-start; justify-content: space-between; }
.workbench h2, .questions > h2 { margin: 0 0 10px; font-size: clamp(1.5rem, 3vw, 2.2rem); letter-spacing: -0.035em; }
.workbench-head p:last-child { max-width: 700px; margin: 0 0 22px; color: var(--muted); }
.editor-badge { padding: 5px 9px; color: #b6dcca; background: var(--code); border-radius: 6px; font-family: ui-monospace, monospace; font-size: 0.75rem; }
.exercise-guide { margin: 0 0 24px; padding: clamp(14px, 2vw, 20px); background: var(--paper); border: 1px solid var(--line); border-radius: 12px; }
.exercise-guide img { display: block; width: 100%; height: auto; border-radius: 8px; }
.exercise-guide figcaption { margin-top: 12px; color: var(--muted); font-size: 0.88rem; line-height: 1.55; }
.code-editor {
  display: block;
  width: 100%;
  min-height: 390px;
  resize: vertical;
  padding: 24px;
  color: #e8f2ed;
  caret-color: var(--yellow);
  background: var(--code);
  border: 2px solid var(--code);
  border-radius: 12px;
  outline: none;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.85rem;
  line-height: 1.7;
  tab-size: 4;
}

.CodeMirror {
  height: 390px;
  color: #e8f2ed;
  background: var(--code);
  border: 2px solid var(--code);
  border-radius: 12px;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
  font-size: 0.85rem;
  line-height: 1.7;
}
.CodeMirror-focused { border-color: var(--green-bright); box-shadow: 0 0 0 3px rgba(31, 106, 84, 0.15); }
.CodeMirror-gutters { background: #111a18; border-right: 1px solid #2d3b37; }
.CodeMirror-linenumber { color: #61736b; }
.CodeMirror-cursor { border-left-color: var(--yellow); }
.CodeMirror-selected { background: #315147 !important; }
.cm-s-liquidjava .cm-comment { color: #80968c; font-style: italic; }
.cm-s-liquidjava .cm-keyword { color: #f08a5d; font-weight: 650; }
.cm-s-liquidjava .cm-atom,
.cm-s-liquidjava .cm-number { color: #d6a6f2; }
.cm-s-liquidjava .cm-def,
.cm-s-liquidjava .cm-variable-2,
.cm-s-liquidjava .cm-variable-3 { color: #86c7ed; }
.cm-s-liquidjava .cm-variable { color: #e8f2ed; }
.cm-s-liquidjava .cm-property { color: #abdac5; }
.cm-s-liquidjava .cm-operator { color: #abdac5; }
.cm-s-liquidjava .cm-string,
.cm-s-liquidjava .cm-string-2 { color: #f3c75f; }
.cm-s-liquidjava .cm-meta,
.cm-s-liquidjava .cm-qualifier { color: #9fe0c0; }
.cm-s-liquidjava .cm-type,
.cm-s-liquidjava .cm-builtin { color: #86c7ed; }
.cm-s-liquidjava .cm-tag,
.cm-s-liquidjava .cm-error { color: #ef8a62; }
.CodeMirror-matchingbracket { color: var(--yellow) !important; text-decoration: underline; }
.editor-actions { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; margin-top: 16px; }
.text-button { margin-left: auto; color: var(--green-bright); }

.exercise-feedback { margin-top: 18px; padding: 14px 16px; color: var(--muted); background: var(--paper); border-left: 4px solid #bdb8ad; border-radius: 5px; }
.exercise-feedback p, .exercise-feedback ul { margin: 0; }
.exercise-feedback ul { padding-left: 20px; }
.exercise-feedback.is-success { color: #164938; background: #e6f5ed; border-color: #2a8a68; }
.exercise-feedback.is-error { color: #7c3424; background: #fff0e9; border-color: var(--orange); }
.solution-panel { margin-top: 22px; }
.solution-heading { display: flex; justify-content: space-between; margin-bottom: 10px; font-size: 0.85rem; }
.solution-heading span { color: var(--muted); }
.solution-panel pre { box-shadow: none; }

.questions { display: grid; gap: 18px; }
.question-card { margin: 0; padding: 24px 0 0; border: 0; border-top: 1px solid var(--line); }
.question-heading { display: flex; gap: 13px; align-items: flex-start; }
.question-heading > span { display: grid; flex: 0 0 auto; width: 25px; height: 25px; place-items: center; color: var(--green); background: var(--mint); border-radius: 50%; font-family: ui-monospace, monospace; font-size: 0.72rem; font-weight: bold; }
.question-heading h3 { margin: 1px 0 16px; font-size: 1rem; }
.option-list { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 9px; margin-left: 38px; }
.option { display: flex; gap: 10px; align-items: flex-start; padding: 11px 12px; background: var(--paper); border: 1px solid transparent; border-radius: 7px; cursor: pointer; }
.option:hover { border-color: #acb8b1; }
.option:has(input:checked) { color: var(--green); background: #e5f3eb; border-color: #7fa996; }
.option input { margin-top: 4px; accent-color: var(--green-bright); }
.answer-input {
  width: calc(100% - 38px);
  margin-left: 38px;
  padding: 13px 14px;
  color: var(--ink);
  background: var(--white);
  border: 1px solid #bdb9ae;
  border-radius: 8px;
  outline: none;
}
.answer-input:focus { border-color: var(--green-bright); box-shadow: 0 0 0 3px rgba(31, 106, 84, 0.15); }
.question-feedback { min-height: 22px; margin: 8px 0 0 38px; font-size: 0.84rem; }
.question-feedback p { margin: 0; }
.question-feedback .correct { color: #21704f; }
.question-feedback .incorrect { color: #a54831; }

.lesson-footer { display: flex; gap: 18px; align-items: center; justify-content: space-between; padding-top: 8px; }
.lesson-footer > span { color: var(--muted); font-size: 0.82rem; }
.finish-mark { display: grid; width: 74px; height: 74px; place-items: center; color: var(--green); background: var(--mint); border-radius: 50%; font-size: 2rem; font-weight: 800; }
.finished-message { display: flex; gap: 13px; align-items: center; }
.finished-message > span { display: grid; width: 38px; height: 38px; place-items: center; color: var(--green); background: var(--mint); border-radius: 50%; font-weight: 900; }
.finished-message p { margin: 2px 0 0; color: var(--muted); font-size: 0.82rem; }

.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; }
.noscript { margin: 20px; padding: 20px; color: #792f1e; background: #fff0e9; border: 1px solid #e9a28e; }

@media (max-width: 920px) {
  .tutorial-shell { grid-template-columns: 1fr; }
  .tutorial-nav { position: static; height: auto; padding: 18px 22px; border-right: 0; border-bottom: 1px solid var(--line); }
  .tutorial-nav > .eyebrow, .progress-summary p { display: none; }
  .step-list { grid-template-columns: repeat(5, minmax(60px, 1fr)); }
  .step-button { justify-content: center; padding: 7px 4px; font-size: 0.72rem; }
  .step-button { flex-direction: column; gap: 4px; text-align: center; }
  .progress-summary { margin-top: 12px; padding-top: 0; border-top: 0; }
  .tutorial-main { padding: 36px 22px 60px; }
  .welcome-card { grid-template-columns: 1fr; }
  .concept-grid { grid-template-columns: 1fr; }
}

@media (max-width: 600px) {
  .site-header { min-height: 66px; padding: 10px 16px; }
  .brand-mark { width: 38px; height: 38px; }
  .brand small { display: none; }
  .tutorial-nav { top: 66px; overflow-x: auto; padding: 12px; }
  .step-list { min-width: 430px; }
  .progress-summary { min-width: 430px; }
  .welcome-copy, .route-card { padding: 30px 24px; }
  .welcome-card, .workbench, .questions { border-radius: 13px; }
  h1 { font-size: 2.45rem; }
  .lesson-number { display: none; }
  .workbench, .questions { padding: 23px 18px; }
  .code-editor { min-height: 430px; padding: 16px; font-size: 0.76rem; }
  .CodeMirror { height: 430px; font-size: 0.76rem; }
  .option-list, .answer-input, .question-feedback { margin-left: 0; width: 100%; }
  .option-list { grid-template-columns: 1fr; }
  .editor-actions .text-button { width: 100%; margin-left: 0; }
  .lesson-footer { align-items: stretch; flex-direction: column; }
  .lesson-footer > span { display: none; }
  .lesson-footer .primary-button, .lesson-footer .secondary-button { width: 100%; }
  .solution-heading { align-items: flex-start; flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; }
}