:root {
  --bg-page: #0a0f22;
  --bg-stage: #0e1430;
  --bg-card: #161c3b;
  --bg-card-strong: #1c2454;
  --bg-panel: #10162f;
  --edge: #2a3158;
  --edge-soft: #1e2444;
  --ink: #e7eaf6;
  --ink-soft: #aab2dc;
  --ink-muted: #717ba8;
  --accent: #7a81ff;
  --accent-soft: rgba(122, 129, 255, 0.18);
  --warn: #f59e0b;
  --good: #45d18c;
  --bad: #ef4f6b;
  --shadow: 0 18px 40px -16px rgba(0, 0, 0, 0.6);
  --radius: 14px;
}

html, body {
  margin: 0;
  min-height: 100%;
  background: var(--bg-page);
  color: var(--ink);
  font: 14px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

main {
  max-width: 720px;
  margin: 0 auto;
  padding: 16px 24px 80px;
}

/* ============================================================ */
/* topbar above the stage: lesson controls only               */
/* ============================================================ */

.stage-topbar {
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 8px;
  margin-bottom: 12px;
  padding: 14px 12px 10px;
  background: var(--bg-panel);
  border: 1px solid var(--edge);
  border-radius: var(--radius);
  overflow: hidden;
}

.topbar-progress {
  display: flex;
  align-items: center;
  gap: 10px;
  min-width: 0;
}

.lesson-step {
  font-size: 10px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  font-weight: 700;
  white-space: nowrap;
  min-width: 78px;
}

/* ============================================================ */
/* stage: a 90s webpage in a faux browser frame               */
/* ============================================================ */

.tutorial-stage {
  position: relative;
  height: 520px;
  background: #c0c0c0;
  border: 3px solid;
  border-color: #fafafa #5b5b5b #5b5b5b #fafafa; /* faux Win95 outset */
  border-radius: 0;
  padding: 0;
  overflow: hidden;
  box-shadow: 6px 6px 0 #2a2410, var(--shadow);
}

/* faux browser title bar across the top of the stage */
.tutorial-stage::before {
  content: "▣  http://www.layout-lint.net/welcome.htm";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 32px;
  display: flex;
  align-items: center;
  padding: 0 14px;
  background: linear-gradient(180deg, #2c43b8 0%, #1a226e 100%);
  color: #dfe8ff;
  font: 700 11.5px "Tahoma", "Geneva", "MS Sans Serif", sans-serif;
  letter-spacing: 0.05em;
  border-bottom: 2px solid #fafafa;
  z-index: 2;
}

/* every descendant gets a smooth tween */
.tutorial-stage * {
  transition:
    transform 620ms cubic-bezier(.65, 0, .25, 1),
    opacity 380ms ease,
    width 480ms cubic-bezier(.65, 0, .25, 1),
    color 280ms ease,
    background 280ms ease,
    font-weight 200ms ease;
}

#page {
  position: absolute;
  top: 38px;
  left: 6px;
  right: 6px;
  bottom: 38px;
  padding: 0 18px 12px;
  background:
    radial-gradient(circle at 18% 30%, #eef4ff 0%, transparent 46%),
    #f3f6ff;
  border: 2px solid #1a226e;
  border-radius: 0;
  display: grid;
  grid-template-rows: auto auto auto minmax(150px, 170px) auto;
  gap: 8px;
}

#page-header {
  position: relative;
  display: flex;
  align-items: center;
  gap: 10px;
  margin: 0 -18px 4px;
  padding: 6px 14px;
  background: linear-gradient(180deg, #1a226e 0%, #2c43b8 100%);
  border-bottom: 3px solid #9fb4ff;
}

#headline {
  flex: 1;
  margin: 0;
  font-family: "Comic Sans MS", "Comic Neue", "Chalkboard SE", cursive;
  font-size: 20px;
  font-weight: 400;
  letter-spacing: -0.01em;
  color: #dfe8ff;
  text-shadow: 2px 2px 0 #163a8c;
}

#subhead {
  margin: 0;
  font-family: "Georgia", "Times New Roman", serif;
  font-style: italic;
  color: #1b2f73;
  font-size: 12px;
}

#badge {
  position: absolute;
  top: 6px;
  right: 14px;
  padding: 6px 14px;
  background: #ff3399;
  color: #fff;
  font-family: "Tahoma", "Geneva", sans-serif;
  font-size: 13px;
  font-weight: 700;
  letter-spacing: 0.14em;
  border: 2px solid #fff;
  border-radius: 0;
  box-shadow: 3px 3px 0 #870056;
  text-transform: uppercase;
  z-index: 5;
}

#nav {
  display: flex;
  gap: 4px;
  padding: 4px 8px;
  background: #1a226e;
  border: 2px solid #9fb4ff;
  border-radius: 0;
  align-self: start;
}

#nav a {
  color: #dfe8ff;
  font-family: "Courier New", Courier, monospace;
  font-size: 12px;
  font-weight: 700;
  text-decoration: underline;
  padding: 0 8px;
}

#card-row {
  display: flex;
  gap: 14px;
  align-self: stretch;
}

.card {
  flex: 1;
  background: #ffffff;
  border-radius: 0;
  padding: 12px;
  border: 3px solid #00aaff;
  box-shadow: 4px 4px 0 #005c8a;
  display: grid;
  grid-template-rows: auto auto auto;
  gap: 6px;
  min-width: 0;
}

#card-b { border-color: #ff3399; box-shadow: 4px 4px 0 #870056; }
#card-c { border-color: #33cc99; box-shadow: 4px 4px 0 #1f7a59; }

.card-img {
  height: 44px;
  width: 30%;
  background: repeating-linear-gradient(45deg, #00aaff 0 8px, #dce8ff 8px 16px);
  border: 1px solid #1a226e;
  border-radius: 0;
}

#card-b .card-img {
  background: repeating-linear-gradient(45deg, #ff3399 0 8px, #dce8ff 8px 16px);
}

#card-c .card-img {
  background: repeating-linear-gradient(45deg, #33cc99 0 8px, #dce8ff 8px 16px);
}

.card h3 {
  margin: 0;
  font-family: "Verdana", "Geneva", sans-serif;
  font-size: 13px;
  font-weight: 700;
  color: #00658f;
}

#card-b h3 { color: #870056; }
#card-c h3 { color: #1f7a59; }

.card p {
  margin: 0;
  font-family: "Georgia", "Times New Roman", serif;
  font-size: 11.5px;
  color: #1a226e;
  line-height: 1.4;
}

/* card-c reserves space from the start, invisible until lesson 6 */
#card-c {
  opacity: 0;
  transform: scale(0.85);
  pointer-events: none;
}

#footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 8px 12px;
  background: #1a226e;
  border: 2px solid #ffe680;
  border-radius: 0;
  font-family: "Courier New", Courier, monospace;
  font-size: 11.5px;
  color: #ffe680;
}

#popover {
  background: #ffe680;
  color: #1a226e;
  padding: 4px 10px;
  border: 2px dashed #d6005c;
  border-radius: 0;
  font-family: "Comic Sans MS", "Comic Neue", cursive;
  font-size: 11px;
  font-weight: 700;
}

/* ============================================================ */
/* broken initial state: each lesson fixes exactly one thing  */
/* ============================================================ */

/* lesson 1 (swap): cards a and b swap via translate so the
   transition can animate them, card-a also sits lower (lesson 2) */
.tutorial-stage #card-a { transform: translateX(calc(100% + 14px)) translateY(26px); }
.tutorial-stage #card-b { transform: translateX(calc(-100% - 14px)); }

/* lesson 3 (containment): badge drifts into the status-bar strip, tilted */
.tutorial-stage #badge { transform: translate(-540px, 430px) rotate(-9deg); }

/* lesson 5 (percentages): card-a's image is a stub width */
.tutorial-stage #card-a-image { width: 30%; }

/* lesson 6 (count): card-c is invisible, declared above */

/* lesson 7 (text + css): headline reads "Hi" with default weight */

/* lesson 8 (negation): popover sits inside the footer */

/* === per-lesson fixes, cumulative via data attributes === */

.tutorial-stage[data-lesson1-done] #card-a { transform: translateX(0) translateY(26px); }
.tutorial-stage[data-lesson1-done] #card-b { transform: translateX(0); }
.tutorial-stage[data-lesson2-done] #card-a { transform: translateX(0) translateY(0); }
.tutorial-stage[data-lesson3-done] #badge { transform: translate(0, 0) rotate(0); }
.tutorial-stage[data-lesson5-done] #card-a-image {
  /* span the full card box: 12px padding + 3px border each side */
  width: calc(100% + 30px);
  margin-left: -15px;
  margin-right: -15px;
}
.tutorial-stage[data-lesson6-done] #card-c {
  opacity: 1;
  transform: scale(1);
  pointer-events: auto;
}
.tutorial-stage[data-lesson7-done] #headline { font-weight: 700; }
.tutorial-stage[data-lesson8-done] #popover {
  position: absolute;
  top: 14px;
  right: 110px;
  background: #33cc99;
  color: #fff;
  border: 2px solid #fff;
  box-shadow: 3px 3px 0 #1f7a59;
}

/* lesson 4 pulse highlight, triggered in JS */
@keyframes pulse-ring {
  0%   { box-shadow: 0 0 0 0 rgba(122, 129, 255, 0.55), 0 0 0 1px var(--edge); }
  60%  { box-shadow: 0 0 0 10px rgba(122, 129, 255, 0), 0 0 0 1px var(--edge); }
  100% { box-shadow: 0 0 0 0 rgba(122, 129, 255, 0), 0 0 0 1px var(--edge); }
}
.tutorial-stage .pulsing {
  animation: pulse-ring 1100ms ease-out;
}

/* ============================================================ */
/* lesson body, nested inside the topbar                      */
/* ============================================================ */

.lesson-body {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 12px 14px;
  background: rgba(0, 0, 0, 0.18);
  border: 1px solid var(--edge-soft);
  border-radius: 10px;
  min-height: 204px;
}

#lesson-title {
  margin: 0;
  font-size: 16px;
  font-weight: 600;
  color: var(--ink);
}

#lesson-prose {
  margin: 0;
  color: var(--ink-soft);
  font-size: 13px;
}

#lesson-prose code {
  display: inline-block;
  padding: 1px 5px 2px;
  border: 1px solid rgba(122, 129, 255, 0.34);
  border-radius: 5px;
  background: rgba(122, 129, 255, 0.14);
  color: #cdd6ff;
  font: 12px/1.25 "SF Mono", ui-monospace, "Cascadia Mono", Menlo, Consolas, monospace;
}

/* the rule card is a torn-out strip of the spec editor: gutter,
   line numbers, token colours, no rounding */
#lesson-rule {
  margin: 4px 0 0;
  padding: 0;
  background: #050a1d;
  border: 1px solid rgba(122, 129, 255, 0.28);
  font: 12.5px/1.7 "SF Mono", ui-monospace, "Cascadia Mono", Menlo, Consolas, monospace;
  color: #cdd6ff;
  overflow-x: auto;
}

.rl-head {
  display: flex;
  justify-content: space-between;
  padding: 3px 10px;
  border-bottom: 1px solid rgba(122, 129, 255, 0.2);
  font-size: 9px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-muted);
}

.rl-body {
  display: block;
  padding: 5px 0;
}

.rl-line {
  display: flex;
}

.rl-no {
  flex: none;
  width: 32px;
  padding-right: 8px;
  text-align: right;
  color: #3a4575;
  border-right: 1px solid rgba(122, 129, 255, 0.16);
  user-select: none;
}

.rl-code {
  padding: 0 12px;
  white-space: pre;
}

.tok-kw { color: #9da5ff; }
.tok-num { color: #45d18c; }
.tok-str { color: #e8c06a; }
.tok-punc { color: #5c689f; }

#lesson-rule.empty {
  color: var(--ink-muted);
  font-style: italic;
}

#lesson-actions {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-top: auto;
  padding-top: 6px;
}

#lesson-apply,
#lesson-reset {
  font-family: inherit;
  font-size: 12px;
  font-weight: 600;
  padding: 8px 14px;
  border-radius: 8px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: #fff;
  cursor: pointer;
  transition: background 180ms ease, border-color 180ms ease, color 180ms ease;
}

#lesson-apply:hover:not(:disabled) {
  background: #9097ff;
  border-color: #9097ff;
}

#lesson-apply:disabled {
  opacity: 0.4;
  cursor: default;
}

#lesson-reset {
  background: transparent;
  color: var(--ink-muted);
  border-color: var(--edge-soft);
}

#lesson-reset:hover {
  background: rgba(255, 255, 255, 0.05);
  color: var(--ink-soft);
  border-color: var(--edge);
}

.lesson-rail {
  display: flex;
  gap: 3px;
  flex: 1;
  min-width: 0;
}

.step {
  flex: 1;
  font-family: inherit;
  font-size: 10px;
  font-weight: 700;
  padding: 3px 0;
  border-radius: 4px;
  border: 1px solid var(--edge-soft);
  background: transparent;
  color: var(--ink-muted);
  cursor: pointer;
  transition: background 160ms ease, color 160ms ease, border-color 160ms ease;
}

.step:hover { background: rgba(255, 255, 255, 0.04); color: var(--ink-soft); }
.step.done { background: rgba(69, 209, 140, 0.16); color: var(--good); border-color: rgba(69, 209, 140, 0.35); }
.step.active { background: var(--accent-soft); color: var(--ink); border-color: var(--accent); }
.step.done.active {
  background: rgba(69, 209, 140, 0.28);
  color: var(--good);
  border-color: var(--good);
}

.lesson-progress {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--edge-soft);
  overflow: hidden;
}

#progress-bar {
  width: 0%;
  height: 100%;
  background: linear-gradient(90deg, var(--accent), var(--good));
  transition: width 400ms cubic-bezier(.65, 0, .25, 1);
}

/* ============================================================ */
/* finale message slides in when the lessons are complete     */
/* ============================================================ */

.lesson-body.finale #lesson-rule,
.lesson-body.intro #lesson-rule {
  display: none;
}

.lesson-body.finale #lesson-title {
  font-size: 14px;
  line-height: 1.25;
}

.lesson-body.finale #lesson-prose {
  font-size: 11.5px;
  line-height: 1.45;
  flex: 1 1 auto;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 14px;
}

.finale-recap {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 10px 28px;
  margin: 0 auto;
  width: min(640px, 100%);
  padding: 0;
  list-style: none;
  font-size: 11px;
  color: var(--ink-soft);
}
.finale-recap li {
  display: flex;
  flex-direction: column;
  gap: 0;
}
.finale-recap strong {
  color: var(--ink);
  font-size: 11px;
  font-weight: 700;
}
.finale-recap span {
  color: var(--ink-muted);
  font-size: 10.5px;
  line-height: 1.32;
}

.playground-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 8px;
  color: var(--accent);
  text-decoration: none;
  font-size: 13px;
  font-weight: 600;
}
.playground-link:hover { text-decoration: underline; }