/* Experience page (About our PI). Design tokens only, no inline styles (the site's content security policy forbids them).
   experience.js gives the hero a scroll progress --p and the stack a step and an explosion --x; the rules below turn
   them into motion. Motion tiers follow the header: html[data-motion] is full, lite (fades only) or static (everything
   shown at rest). With no script, or on a small or short screen, the stack is an ordinary page of four panels. */

body[data-page="experience"] main { max-width: none; padding: 0; }
.xp { --xp-dark: color-mix(in srgb, var(--midnight) 52%, var(--ink-0)); --xp-ink: var(--chart-white); --xp-mute: color-mix(in srgb, var(--chart-white) 70%, transparent); overflow-x: clip; }
.xp *, .xp *::before, .xp *::after { box-sizing: border-box; }
.xp p { margin: 0 0 var(--space-4); }
.xp p, .xp li { text-wrap: pretty; }
.xp a:focus-visible, .xp button:focus-visible { outline: var(--focus-width) solid var(--focus-ring); outline-offset: var(--focus-offset); }
[data-accent="ember"] { --ac: var(--ember); } [data-accent="amber"] { --ac: var(--amber); } [data-accent="verde"] { --ac: var(--verde); } [data-accent="cobalt"] { --ac: var(--sky); }
.xp [data-g="systems"] { --ac: var(--ember); } .xp [data-g="scripting"] { --ac: var(--amber); } .xp [data-g="science"] { --ac: var(--verde); } .xp [data-g="web"] { --ac: var(--sky); }

/* progress: at rest (no script, or Off) every scene is complete; with script it starts at 0 */
.xp [data-scene] { --p: 1; }
html.xp-js:not([data-motion="static"]) .xp [data-scene] { --p: 0; }

.xp-in { max-width: 1160px; margin: 0 auto; padding: 0 clamp(16px, 4vw, 32px); position: relative; }
.xp-narrow { max-width: 780px; }
.xp-k { margin: 0 0 var(--space-3); font: var(--type-label); letter-spacing: var(--type-label-tracking); text-transform: uppercase; color: var(--text-secondary); }
.xp-h2 { margin: 0 0 var(--space-4); font: 600 clamp(1.9rem, 4.4vw, 3.3rem)/1.08 var(--font-display); letter-spacing: -0.015em; text-wrap: balance; }
.xp-lead { max-width: 64ch; font-size: clamp(1.05rem, 1.5vw, 1.2rem); line-height: 1.6; color: var(--text-secondary); }

/* reveal on scroll */
html.xp-js:not([data-motion="static"]) .xp .xp-rv { opacity: 0; transform: translateY(22px); transition: opacity 700ms var(--ease), transform 700ms var(--ease); }
html.xp-js:not([data-motion="static"]) .xp .xp-rv.xp-on { opacity: 1; transform: none; }
html[data-motion="lite"].xp-js .xp .xp-rv { transform: none; }

/* ---------- hero: a terminal, drifting code and an ECG trace ---------- */
.xp-hero { position: relative; min-height: min(100svh, 58rem); display: grid; align-items: center; padding: clamp(64px, 11vh, 120px) clamp(16px, 5vw, 72px) clamp(120px, 18vh, 190px);
  color: var(--xp-ink); overflow: hidden;
  background: radial-gradient(55% 70% at 88% 20%, color-mix(in srgb, var(--cobalt) 38%, transparent), transparent 70%), radial-gradient(45% 60% at 4% 100%, color-mix(in srgb, var(--verde) 22%, transparent), transparent 70%), var(--xp-dark); }
.xp-grid { position: absolute; inset: 0; opacity: 0.5; background-image: linear-gradient(color-mix(in srgb, var(--sky) 14%, transparent) 1px, transparent 1px), linear-gradient(90deg, color-mix(in srgb, var(--sky) 14%, transparent) 1px, transparent 1px); background-size: 56px 56px; mask-image: radial-gradient(80% 70% at 50% 40%, #000, transparent); transform: translateY(calc(var(--p) * -40px)); }
.xp-toks { position: absolute; inset: 0; pointer-events: none; transform: translateY(calc(var(--p) * -90px)); mask-image: linear-gradient(90deg, rgba(0, 0, 0, 0.18), #000 62%); }
.xp-tok { position: absolute; font: 500 clamp(12px, 1.2vw, 15px)/1 var(--font-code); white-space: nowrap; color: color-mix(in srgb, var(--sky) 60%, transparent); opacity: 0.45; }
.xp-tok:nth-child(1) { left: 4%; top: 12%; } .xp-tok:nth-child(2) { left: 22%; top: 70%; } .xp-tok:nth-child(3) { left: 40%; top: 8%; } .xp-tok:nth-child(4) { left: 58%; top: 80%; }
.xp-tok:nth-child(5) { left: 8%; top: 44%; } .xp-tok:nth-child(6) { left: 74%; top: 14%; } .xp-tok:nth-child(7) { left: 30%; top: 36%; } .xp-tok:nth-child(8) { left: 82%; top: 62%; }
.xp-tok:nth-child(9) { left: 50%; top: 56%; } .xp-tok:nth-child(10) { left: 90%; top: 40%; } .xp-tok:nth-child(11) { left: 14%; top: 88%; } .xp-tok:nth-child(12) { left: 66%; top: 44%; }
.xp-tok:nth-child(13) { left: 36%; top: 92%; } .xp-tok:nth-child(14) { left: 92%; top: 84%; }
html[data-motion="full"] .xp-tok { animation: xp-drift 9s ease-in-out infinite alternate; }
.xp-tok:nth-child(3n) { animation-delay: -3s; } .xp-tok:nth-child(3n+1) { animation-delay: -6s; animation-duration: 12s; } .xp-tok:nth-child(5n) { color: color-mix(in srgb, var(--verde) 62%, transparent); }
@keyframes xp-drift { from { transform: translate3d(0, 10px, 0); opacity: 0.25; } to { transform: translate3d(8px, -18px, 0); opacity: 0.6; } }

.xp-hero-in { position: relative; z-index: 2; width: 100%; max-width: 52rem; }
.xp-eyebrow { margin: 0 0 var(--space-1); font: var(--type-label); letter-spacing: var(--type-label-tracking); text-transform: uppercase; color: var(--verde); }
.xp-hero h1 { margin: 0 0 var(--space-6); font: 600 clamp(1rem, 1.3vw, 1.1rem)/1.3 var(--font-ui); letter-spacing: 0.01em; color: color-mix(in srgb, var(--xp-ink) 92%, transparent); }
.xp-term { border: 1px solid color-mix(in srgb, var(--chart-white) 22%, transparent); border-radius: var(--radius-ui); background: color-mix(in srgb, var(--ink-0) 62%, transparent); box-shadow: 0 24px 60px color-mix(in srgb, #000 40%, transparent); backdrop-filter: blur(4px); }
.xp-term-bar { display: flex; align-items: center; gap: 6px; padding: 10px 14px; border-bottom: 1px solid color-mix(in srgb, var(--chart-white) 14%, transparent); font: 500 12px/16px var(--font-code); color: var(--xp-mute); }
.xp-term-bar i { width: 10px; height: 10px; border-radius: 2px; background: color-mix(in srgb, var(--chart-white) 26%, transparent); }
.xp-term-bar i:nth-child(1) { background: var(--signal-red); } .xp-term-bar i:nth-child(2) { background: var(--amber); } .xp-term-bar i:nth-child(3) { background: var(--verde); }
.xp-term-bar span { margin-left: var(--space-3); }
.xp-term-body { padding: var(--space-5) var(--space-5) var(--space-4); font: 400 clamp(1rem, 1.7vw, 1.25rem)/1.65 var(--font-code); }
.xp .xp-term-body p { margin: 0 0 6px; }
.xp-ps { color: var(--verde); margin-right: 0.8ch; }
.xp-cmd { color: var(--xp-ink); font-weight: 500; }
.xp-out { color: var(--xp-mute); padding-left: 1.8ch; }
.xp-ty-on { color: inherit; } .xp-ty-off { color: transparent; }
.xp-caret { display: inline-block; width: 0.6em; height: 1.05em; vertical-align: text-bottom; background: var(--verde); }
html[data-motion="full"] .xp-caret { animation: xp-blink 1.1s steps(1) infinite; }
@keyframes xp-blink { 50% { opacity: 0; } }
.xp-typing .xp-ty-on::after { content: ""; display: inline-block; width: 0.6em; height: 1.05em; margin-left: 1px; vertical-align: text-bottom; background: var(--verde); }
.xp-cue { display: inline-flex; align-items: center; gap: var(--space-2); min-height: 44px; margin-top: var(--space-6); padding: 0 var(--space-4); border: 1px solid color-mix(in srgb, var(--xp-ink) 40%, transparent); border-radius: var(--radius-ui); color: var(--xp-ink); text-decoration: none; font: 600 15px/20px var(--font-ui); }
.xp-cue:hover { background: color-mix(in srgb, var(--xp-ink) 12%, transparent); }
html[data-motion="full"] .xp-cue svg { animation: xp-bob 2.2s var(--ease) infinite; }
@keyframes xp-bob { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(4px); } }


.xp-ecg { position: absolute; left: 0; right: 0; bottom: 0; width: 100%; height: clamp(90px, 16vh, 150px); z-index: 1; pointer-events: none; }
.xp-ecg path { fill: none; stroke-linejoin: round; stroke-linecap: round; vector-effect: non-scaling-stroke; }
.xp-ecg-ghost { stroke: color-mix(in srgb, var(--verde) 28%, transparent); stroke-width: 1.5; }
.xp-ecg-line { stroke: var(--verde); stroke-width: 2.4; filter: drop-shadow(0 0 6px var(--verde)); }
html[data-motion="full"] .xp-ecg-line { stroke-dasharray: 11 89; animation: xp-sweep 4.8s linear infinite; }
@keyframes xp-sweep { from { stroke-dashoffset: 11; } to { stroke-dashoffset: -89; } }
html[data-motion="lite"] .xp-ecg-line { stroke-dasharray: none; opacity: 0.8; }

/* ---------- the stack: four layers, built from the foundation up ---------- */
.xp-stack { position: relative; padding: clamp(72px, 10vw, 120px) 0; color: var(--xp-ink); background: linear-gradient(180deg, var(--xp-dark), color-mix(in srgb, var(--ink-1) 70%, var(--midnight))); }
.xp-stack .xp-k, .xp-stack .xp-lead { color: var(--xp-mute); }
.xp-stack .xp-k { color: var(--verde); }
.xp-stack-head { max-width: 52rem; margin-bottom: var(--space-6); }
.xp-stack-head .xp-h2 { margin-bottom: var(--space-3); }
.xp-stage { display: grid; grid-template-columns: minmax(0, 0.9fr) minmax(0, 1.1fr); gap: var(--space-8); align-items: center; }

.xp-slabs { position: relative; height: clamp(300px, 52vh, 460px); perspective: 1500px; perspective-origin: 50% 10%; --x: 1; }
.xp-iso { position: absolute; inset: 0; transform-style: preserve-3d; transform: translateY(6%) rotateX(58deg) rotateZ(-38deg); }
.xp-slab { --s: clamp(190px, 24vw, 290px); position: absolute; left: 50%; top: 50%; width: var(--s); height: var(--s); margin: calc(var(--s) / -2) 0 0 calc(var(--s) / -2);
  transform: translateZ(calc((var(--i) - 2.5) * (16px + var(--x) * 74px)));
  border: 1px solid color-mix(in srgb, var(--ac) 55%, transparent); border-radius: 3px; opacity: 0.55;
  background: linear-gradient(135deg, color-mix(in srgb, var(--ac) 30%, var(--ink-1)), color-mix(in srgb, var(--ac) 10%, var(--ink-0)));
  box-shadow: 0 0 0 1px color-mix(in srgb, #000 40%, transparent), 0 22px 28px color-mix(in srgb, #000 35%, transparent);
  transition: opacity 500ms var(--ease), box-shadow 500ms var(--ease), border-color 500ms var(--ease); }
.xp-slab[data-i="1"] { --i: 1; } .xp-slab[data-i="2"] { --i: 2; } .xp-slab[data-i="3"] { --i: 3; } .xp-slab[data-i="4"] { --i: 4; }
.xp-stack[data-step="1"] .xp-slab[data-i="1"], .xp-stack[data-step="2"] .xp-slab[data-i="2"], .xp-stack[data-step="3"] .xp-slab[data-i="3"], .xp-stack[data-step="4"] .xp-slab[data-i="4"] { opacity: 1; border-color: var(--ac); box-shadow: 0 0 46px color-mix(in srgb, var(--ac) 60%, transparent), 0 22px 28px color-mix(in srgb, #000 35%, transparent); }
html.xp-js .xp-slabs.xp-flat .xp-slab { opacity: 0.9; }
.xp-pcb { position: absolute; inset: 11%; display: grid; grid-template-columns: repeat(4, 1fr); grid-auto-rows: 1fr; gap: 7%; }
.xp-pcb i { border-radius: 2px; background: color-mix(in srgb, var(--ac) 22%, transparent); border: 1px solid color-mix(in srgb, var(--ac) 40%, transparent); transition: background 400ms var(--ease); }
.xp-stack[data-step="1"] .xp-slab[data-i="1"] .xp-pcb i, .xp-stack[data-step="2"] .xp-slab[data-i="2"] .xp-pcb i, .xp-stack[data-step="3"] .xp-slab[data-i="3"] .xp-pcb i, .xp-stack[data-step="4"] .xp-slab[data-i="4"] .xp-pcb i { background: color-mix(in srgb, var(--ac) 70%, transparent); }
html[data-motion="full"] .xp-stack[data-step="1"] .xp-slab[data-i="1"] .xp-pcb i, html[data-motion="full"] .xp-stack[data-step="2"] .xp-slab[data-i="2"] .xp-pcb i, html[data-motion="full"] .xp-stack[data-step="3"] .xp-slab[data-i="3"] .xp-pcb i, html[data-motion="full"] .xp-stack[data-step="4"] .xp-slab[data-i="4"] .xp-pcb i { animation: xp-pulse 1.8s ease-in-out infinite; }
.xp-pcb i:nth-child(3n) { animation-delay: -0.5s; } .xp-pcb i:nth-child(3n+1) { animation-delay: -1.1s; } .xp-pcb i:nth-child(5n) { animation-delay: -1.5s; }
@keyframes xp-pulse { 0%, 100% { opacity: 0.55; } 50% { opacity: 1; } }

.xp-steps { display: flex; flex-wrap: wrap; gap: var(--space-2); margin-bottom: var(--space-5); }
.xp-step { display: inline-flex; align-items: center; gap: var(--space-2); min-height: 44px; padding: 0 var(--space-4); border: 1px solid color-mix(in srgb, var(--xp-ink) 24%, transparent); border-radius: var(--radius-ui); background: transparent; color: var(--xp-mute); font: 600 14px/20px var(--font-ui); cursor: pointer; transition: background 250ms var(--ease), color 250ms var(--ease), border-color 250ms var(--ease); }
.xp-step b { display: inline-grid; place-items: center; width: 22px; height: 22px; border-radius: 3px; background: color-mix(in srgb, var(--ac) 30%, transparent); color: var(--xp-ink); font: 700 12px/1 var(--font-ui); }
.xp-step:hover { color: var(--xp-ink); border-color: var(--ac); }
.xp-step[aria-current="step"] { color: var(--xp-ink); border-color: var(--ac); background: color-mix(in srgb, var(--ac) 22%, transparent); }
.xp-step[aria-current="step"] b { background: var(--ac); color: var(--ink-0); }

.xp-panels { display: grid; }
.xp-panel { grid-area: 1 / 1; padding: var(--space-5) var(--space-6); border: 1px solid color-mix(in srgb, var(--xp-ink) 16%, transparent); border-left: 3px solid var(--ac); border-radius: 3px; background: color-mix(in srgb, var(--ink-0) 40%, transparent); margin-bottom: var(--space-4); }
.xp-panel-n { margin: 0 0 var(--space-2); font: var(--type-label); letter-spacing: var(--type-label-tracking); text-transform: uppercase; color: var(--ac); }
.xp-panel h3 { margin: 0 0 var(--space-3); font: 600 clamp(1.3rem, 2.4vw, 1.75rem)/1.2 var(--font-display); text-wrap: balance; }
.xp .xp-panel p:not(.xp-panel-n) { color: color-mix(in srgb, var(--xp-ink) 84%, transparent); line-height: 1.6; }
.xp-chips, .xp-all { display: flex; flex-wrap: wrap; gap: var(--space-2); margin: var(--space-4) 0 0; padding: 0; list-style: none; }
.xp-chip { padding: 4px 10px; border: 1px solid color-mix(in srgb, var(--ac) 60%, transparent); border-radius: 3px; background: color-mix(in srgb, var(--ac) 14%, transparent); font: 500 13px/20px var(--font-code); }
.xp-panel .xp-chip { color: var(--xp-ink); }

/* with script, motion allowed, a wide and tall enough screen: the stack pins and the panels take turns */
@media (min-width: 900px) and (min-height: 640px) {
  html.xp-js:not([data-motion="static"]) .xp-stack { height: 430vh; padding: 0; }
  html.xp-js:not([data-motion="static"]) .xp-pin { position: sticky; top: 0; height: 100svh; display: flex; align-items: center; }
  html.xp-js:not([data-motion="static"]) .xp-pin > .xp-in { width: 100%; }
  html.xp-js:not([data-motion="static"]) .xp-stack-head { margin-bottom: var(--space-4); }
  html.xp-js:not([data-motion="static"]) .xp-panel { opacity: 0; transform: translateY(14px); pointer-events: none; margin-bottom: 0; transition: opacity 450ms var(--ease), transform 450ms var(--ease); }
  html.xp-js:not([data-motion="static"]) .xp-panel[data-on="true"] { opacity: 1; transform: none; pointer-events: auto; }
  html.xp-js[data-motion="lite"] .xp-panel { transform: none; }
}
/* otherwise: no pin, four panels one after another, slabs exploded and the steps hidden */
@media not all and (min-width: 900px) and (min-height: 640px) { .xp-steps { display: none; } }
html:not(.xp-js) .xp-steps, html[data-motion="static"] .xp-steps { display: none; }
@media (max-width: 899px) { .xp-stage { grid-template-columns: 1fr; } .xp-slabs { height: clamp(260px, 52vw, 340px); margin-top: var(--space-8); } .xp-panels { display: block; } .xp-panel { margin-bottom: var(--space-4); } }

/* ---------- choose the problem ---------- */
.xp-pick { padding: clamp(72px, 10vw, 128px) 0; background: color-mix(in srgb, var(--sky) 7%, var(--surface-page)); }
.xp-bench { margin-top: var(--space-6); }
.xp-probs { display: flex; flex-wrap: wrap; gap: var(--space-2); }
.xp-prob { min-height: 44px; padding: 0 var(--space-4); border: 1px solid var(--border-strong, var(--border-subtle)); border-radius: 3px; background: var(--surface-card); color: var(--text-primary); font: 600 15px/20px var(--font-ui); cursor: pointer; transition: background 200ms var(--ease), color 200ms var(--ease), transform 200ms var(--ease), border-color 200ms var(--ease); }
.xp-prob:hover { border-color: var(--text-primary); }
.xp-prob[aria-checked="true"] { background: var(--text-primary); color: var(--surface-page); border-color: var(--text-primary); }
html[data-motion="full"] .xp-prob:hover { transform: translateY(-2px); }
.xp p.xp-why { min-height: 4.8em; margin: var(--space-6) 0 var(--space-3); max-width: 70ch; font-size: clamp(1.05rem, 1.6vw, 1.25rem); line-height: 1.55; }
.xp-why-k { display: block; margin-bottom: 2px; font: var(--type-label); letter-spacing: var(--type-label-tracking); text-transform: uppercase; color: var(--text-secondary); }
.xp-all { margin-top: var(--space-4); gap: var(--space-3); }
.xp-all li { display: contents; }
.xp-all .xp-chip { cursor: pointer; padding: 6px 12px; font-size: 14px; background: var(--surface-card); border-color: color-mix(in srgb, var(--ac) 45%, var(--border-subtle)); color: var(--text-primary); transition: opacity 300ms var(--ease), transform 300ms var(--ease), background 300ms var(--ease), box-shadow 300ms var(--ease); }
.xp-all .xp-chip.is-on { background: color-mix(in srgb, var(--ac) 26%, var(--surface-card)); border-color: var(--ac); box-shadow: 0 0 0 1px var(--ac); }
.xp-all .xp-chip.is-off { opacity: 0.32; }
html[data-motion="full"] .xp-all .xp-chip.is-on { transform: translateY(-3px); }
html[data-motion="full"] .xp-all .xp-chip.is-off { transform: scale(0.96); }

/* ---------- closing ---------- */
.xp-close { position: relative; padding: clamp(72px, 10vw, 128px) 0; color: var(--xp-ink); background: var(--xp-dark); }
.xp-close .xp-lead { color: var(--xp-mute); }
.xp-go { display: flex; flex-wrap: wrap; gap: var(--space-3); margin-top: var(--space-6); }
.xp-cta { display: inline-flex; align-items: center; min-height: 48px; padding: 0 var(--space-6); border: 1px solid var(--chart-white); border-radius: 3px; background: var(--chart-white); color: var(--midnight); text-decoration: none; font: 700 16px/20px var(--font-ui); transition: transform 200ms var(--ease), background 200ms var(--ease); }
.xp-cta:hover { background: color-mix(in srgb, var(--chart-white) 88%, var(--sky)); }
.xp-cta-2 { background: transparent; color: var(--chart-white); border-color: color-mix(in srgb, var(--chart-white) 50%, transparent); }
.xp-cta-2:hover { background: color-mix(in srgb, var(--chart-white) 12%, transparent); }
html[data-motion="full"] .xp-cta:hover { transform: translateY(-2px); }

@media (max-width: 820px) { .xp-hero { padding-bottom: clamp(110px, 20vh, 160px); } }
@media (prefers-reduced-motion: reduce) { html:not([data-motion]) .xp *, html:not([data-motion]) .xp *::before { animation: none !important; transition: none !important; } }

/* chips on the bench are buttons: pressing one types a sample of its code below */
.xp-all .xp-chip[aria-pressed="true"] { background: var(--ac); color: var(--ink-0); border-color: var(--ac); box-shadow: 0 0 0 2px color-mix(in srgb, var(--ac) 40%, transparent); opacity: 1; }
.xp-all .xp-chip:hover { border-color: var(--ac); }
.xp p.xp-hint { margin: var(--space-4) 0 0; color: var(--text-secondary); font-size: 0.95rem; }

.xp-code { margin-top: var(--space-5); border: 1px solid color-mix(in srgb, var(--chart-white) 20%, transparent); border-radius: 3px; background: var(--xp-dark); color: var(--xp-ink); box-shadow: 0 18px 44px color-mix(in srgb, var(--midnight) 30%, transparent); overflow: hidden; }
.xp-code-bar { display: flex; align-items: center; gap: 6px; padding: 10px 14px; border-bottom: 1px solid color-mix(in srgb, var(--chart-white) 14%, transparent); font: 500 12px/16px var(--font-code); color: var(--xp-mute); }
.xp-code-bar i { width: 10px; height: 10px; border-radius: 2px; background: color-mix(in srgb, var(--chart-white) 26%, transparent); }
.xp-code-bar i:nth-child(1) { background: var(--signal-red); } .xp-code-bar i:nth-child(2) { background: var(--amber); } .xp-code-bar i:nth-child(3) { background: var(--verde); }
.xp-code-file { margin-left: var(--space-3); color: var(--xp-ink); }
.xp-code-lang { margin-left: auto; padding: 1px 8px; border-radius: 3px; background: color-mix(in srgb, var(--ac, var(--sky)) 30%, transparent); color: var(--xp-ink); }
.xp-code-lang:empty { display: none; }
.xp-code-body { margin: 0; min-height: 13.5rem; max-height: 22rem; overflow: auto; padding: var(--space-4) var(--space-5); font: 400 clamp(0.85rem, 1.3vw, 1rem)/1.6 var(--font-code); tab-size: 2; }
.xp-code-text { white-space: pre; }
.xp-code-text.is-empty { color: var(--xp-mute); }
.xp-code-text.is-typing::after { content: ""; display: inline-block; width: 0.6em; height: 1.05em; margin-left: 1px; vertical-align: text-bottom; background: var(--verde); }
.xp p.xp-code-note { margin: var(--space-3) 0 0; color: var(--text-secondary); font-size: 0.9rem; }