/* Lesson 02 · pages, buffer pool, locality. */

#lab-buffer .controls + .controls { margin-top: 10px; }
.st-divider { width: 1px; align-self: stretch; margin: 0 2px; background: var(--line-strong); }

/* Concept-card minis. */
.st-mini-block { position: relative; display: grid; gap: 4px; width: 74px; padding: 14px 8px 8px; border: 1.5px solid var(--line-strong); border-radius: 6px; background: var(--surface); animation: stMiniBlock 3s ease-in-out infinite; }
.st-mini-block span { position: absolute; top: 2px; left: 6px; font-family: var(--mono); font-size: 8.5px; color: var(--muted); }
.st-mini-block i { display: block; height: 6px; border-radius: 3px; background: var(--line); }
.st-mini-block i.want { background: var(--lime); box-shadow: 0 0 0 1px var(--green); }
.st-mini-note { color: var(--muted); font-size: 10.5px; }
@keyframes stMiniBlock { 0%, 30% { transform: none; border-color: var(--line-strong); } 45% { transform: scale(1.1); border-color: var(--green); } 60%, 100% { transform: none; border-color: var(--green); } }

.st-mini-disk, .st-mini-ram { position: relative; padding: 6px 9px; border: 1px solid var(--line-strong); border-radius: 7px; background: var(--surface); font-family: var(--mono); font-size: 10.5px; }
.st-mini-ram { border-color: var(--green); }
.st-mini-ram em { position: absolute; top: -14px; left: 50%; padding: 1px 6px; border-radius: 99px; color: var(--green-deep); background: var(--lime); font-size: 9.5px; font-style: normal; font-weight: 700; opacity: 0; transform: translateX(-50%); animation: stMiniHit 3.2s infinite; }
.st-mini-track { position: relative; width: 58px; height: 22px; }
.st-mini-track b { position: absolute; top: 2px; left: 0; padding: 2px 5px; border-radius: 4px; color: #fff; background: var(--blue); font-family: var(--mono); font-size: 9.5px; animation: stMiniTravel 3.2s infinite; }
@keyframes stMiniTravel { 0% { left: -4px; opacity: 0; } 8% { opacity: 1; } 42% { left: 36px; opacity: 1; } 50%, 100% { left: 36px; opacity: 0; } }
@keyframes stMiniHit { 0%, 58% { opacity: 0; transform: translate(-50%, 4px) scale(.6); } 64%, 90% { opacity: 1; transform: translate(-50%, 0) scale(1); } 100% { opacity: 0; } }

.st-mini-local { flex-direction: column; gap: 5px; }
.st-mini-pair { display: flex; gap: 4px; padding: 5px; border: 1.5px solid var(--line-strong); border-radius: 6px; background: var(--surface); }
.st-mini-pair i, .st-mini-costs em { padding: 2px 6px; border-radius: 4px; font-family: var(--mono); font-size: 10px; font-style: normal; }
.st-mini-pair i { background: var(--surface-soft); }
.st-mini-pair i.a { animation: stMiniA 3.4s infinite; }
.st-mini-pair i.b { animation: stMiniB 3.4s infinite; }
.st-mini-costs { display: flex; gap: 22px; }
.st-mini-costs em.a { color: #8f3d27; background: var(--coral-soft); animation: stMiniCostA 3.4s infinite; }
.st-mini-costs em.b { color: var(--green-deep); background: var(--lime); animation: stMiniCostB 3.4s infinite; }
@keyframes stMiniA { 0%, 10% { background: var(--surface-soft); } 20%, 90% { background: var(--coral-soft); } }
@keyframes stMiniB { 0%, 50% { background: var(--surface-soft); } 58%, 90% { background: var(--lime); } }
@keyframes stMiniCostA { 0%, 12% { opacity: 0; } 22%, 90% { opacity: 1; } 100% { opacity: 0; } }
@keyframes stMiniCostB { 0%, 52% { opacity: 0; transform: scale(.6); } 60%, 90% { opacity: 1; transform: none; } 100% { opacity: 0; } }

/* Lab 02A: shelf of pages and a page opened up. */
.st-anatomy { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr); gap: 22px; align-items: start; }
.st-shelf { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 8px; }
.st-shelf-page { display: grid; gap: 6px; padding: 8px 9px; border: 1.5px solid var(--line-strong); border-radius: 9px; background: var(--surface); box-shadow: 0 2px 0 var(--line); transition: border-color .2s, background .2s; }
.st-shelf-page > b { font-family: var(--mono); font-size: 10px; color: var(--muted); }
.st-shelf-page.open { border-color: var(--green); background: var(--green-soft); }
.st-rows { display: grid; grid-template-columns: repeat(4, 1fr); gap: 4px; }
.st-row { padding: 5px 0; border: 1px solid var(--line); border-radius: 5px; color: var(--ink); background: var(--surface-soft); font-family: var(--mono); font-size: 11px; cursor: pointer; transition: transform .12s, background .15s, border-color .15s; }
.st-row:hover { transform: translateY(-2px); border-color: var(--green); background: var(--green-soft); }
.st-row:active { transform: scale(.92); }
.st-row.fetched { border-color: var(--green); background: var(--lime); font-weight: 500; }
@keyframes stLift { 0% { transform: none; } 30% { transform: translateY(-6px) rotate(-2deg); } 60% { transform: translateY(2px) rotate(1deg); } 100% { transform: none; } }
.st-shelf-page.st-lift { animation: stLift .45s ease-out; }
.st-flying { border-color: var(--green); background: var(--green-soft); }

.st-page { display: flex; flex-direction: column; min-height: 330px; border: 1.5px solid var(--line-strong); border-radius: 10px; background: var(--surface); overflow: hidden; }
.st-page.empty { align-items: center; justify-content: center; border-style: dashed; color: var(--muted); font-size: 13px; }
@keyframes stArrive { 0% { transform: scale(.94, 1.06); } 45% { transform: scale(1.03, .97); } 75% { transform: scale(.99, 1.01); } 100% { transform: none; } }
.st-page.st-arrive { animation: stArrive .5s cubic-bezier(.2, .8, .3, 1.2); }
.st-page-head { display: flex; justify-content: space-between; padding: 8px 12px; color: #fff; background: var(--sidebar); font-family: var(--mono); font-size: 11px; }
.st-page-head span { color: var(--sidebar-muted); }
.st-pointers { display: flex; flex-wrap: wrap; align-items: center; gap: 5px; padding: 8px 12px; border-bottom: 1px dashed var(--line-strong); }
.st-pointers span { padding: 2px 6px; border-radius: 4px; background: var(--blue-soft); color: var(--blue); font-family: var(--mono); font-size: 10.5px; }
.st-pointers span.want { color: var(--green-deep); background: var(--lime); }
.st-pointers small { margin-left: auto; color: var(--muted); font-size: 10px; }
.st-free { flex: 1; display: grid; place-items: center; min-height: 110px; color: var(--muted); font-family: var(--mono); font-size: 11px; background: repeating-linear-gradient(135deg, transparent 0 7px, var(--surface-soft) 7px 14px); }
.st-tuples { display: grid; gap: 4px; padding: 8px; border-top: 1px dashed var(--line-strong); }
.st-tuple { display: grid; grid-template-columns: 38px 1fr auto; gap: 10px; align-items: center; padding: 7px 10px; border-radius: 6px; font-size: 12.5px; animation: stTupleIn .4s cubic-bezier(.2, .8, .3, 1.3) backwards; animation-delay: calc(var(--i) * 70ms + 120ms); }
.st-tuple b { font-family: var(--mono); font-size: 11.5px; }
.st-tuple em { color: var(--muted); font-family: var(--mono); font-size: 10.5px; font-style: normal; }
.st-tuple.want { background: var(--lime); box-shadow: inset 0 0 0 1.5px var(--green); }
.st-tuple.along { background: var(--surface-soft); color: var(--muted); }
.st-tuple.along::after { content: "came along"; grid-column: 2 / 4; margin-top: -4px; font-size: 9.5px; font-weight: 700; letter-spacing: .04em; text-transform: uppercase; color: var(--muted); }
@keyframes stTupleIn { from { opacity: 0; transform: translateY(12px) scale(.9); } }

/* Lab 02B: disk shelf, buffer slots, queue, ledger. */
.bp-stage { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 26px; align-items: start; min-height: 0; }
.bp-shelf { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 8px; }
.bp-card { position: relative; display: grid; gap: 2px; padding: 9px 8px; border: 1.5px solid var(--line-strong); border-radius: 9px; background: var(--surface); box-shadow: 0 3px 0 var(--line); text-align: center; }
.bp-card b { font-family: var(--mono); font-size: 13px; }
.bp-card small { color: var(--muted); font-family: var(--mono); font-size: 9.5px; }
.bp-shelf .bp-card.cached { border-style: dashed; box-shadow: none; opacity: .5; }
.bp-shelf .bp-card.cached::after { content: "in RAM"; position: absolute; top: -8px; right: -6px; padding: 1px 5px; border-radius: 99px; color: var(--green-deep); background: var(--lime); font-size: 8.5px; font-weight: 800; }
@keyframes bpReading { 0%, 100% { transform: none; } 15% { transform: translateX(-3px) rotate(-2deg); } 30% { transform: translateX(3px) rotate(2deg); } 45% { transform: translateX(-2px) rotate(-1deg); } 60% { transform: translateX(2px); } }
.bp-card.bp-reading { border-color: var(--amber); background: linear-gradient(90deg, var(--amber-soft) 0 30%, var(--surface) 60%) 0 0 / 250% 100%; animation: bpReading .45s ease-in-out, bpShimmer .8s linear infinite; }
@keyframes bpShimmer { from { background-position: 100% 0; } to { background-position: -150% 0; } }
.bp-flying { border-color: var(--blue); background: var(--blue-soft); }

.bp-ram { padding: 12px; border: 1.5px solid var(--green); border-radius: 14px; background: color-mix(in srgb, var(--green-soft) 55%, transparent); }
.bp-slots { display: grid; grid-template-columns: repeat(auto-fit, minmax(90px, 1fr)); gap: 10px; }
.bp-slot { position: relative; display: grid; place-items: stretch; min-height: 64px; border: 1.5px dashed var(--line-strong); border-radius: 10px; background: var(--surface); }
.bp-slot > span { align-self: center; justify-self: center; color: var(--muted); font-size: 11px; }
.bp-slot.incoming { border-color: var(--blue); background: var(--blue-soft); }
.bp-slot.incoming > span { color: var(--blue); animation: bpBlink .6s ease-in-out infinite alternate; }
@keyframes bpBlink { to { opacity: .35; } }
.bp-slot .bp-card { margin: -1.5px; }
.bp-card.next-out { border-color: var(--coral); }
.bp-next { position: absolute; bottom: -9px; left: 50%; padding: 1px 7px; border-radius: 99px; color: #fff; background: var(--coral); font-size: 9px; font-style: normal; font-weight: 800; letter-spacing: .03em; transform: translateX(-50%); animation: bpTag .3s cubic-bezier(.2, .8, .3, 1.4); white-space: nowrap; }
@keyframes bpTag { from { transform: translateX(-50%) scale(.4); opacity: 0; } }
@keyframes bpLand { 0% { transform: scale(1.18, .78) translateY(4px); } 35% { transform: scale(.92, 1.1) translateY(-6px); } 60% { transform: scale(1.04, .96); } 80% { transform: scale(.99, 1.01); } 100% { transform: none; } }
.bp-card.bp-land { animation: bpLand .55s cubic-bezier(.2, .8, .3, 1); }
@keyframes bpHit { 0% { transform: scale(1); background: var(--surface); } 30% { transform: scale(1.14) rotate(-3deg); background: var(--lime); box-shadow: 0 0 0 6px rgba(200, 237, 118, .5); } 60% { transform: scale(.97) rotate(2deg); } 100% { transform: none; } }
.bp-card.bp-hit { animation: bpHit .5s cubic-bezier(.2, .8, .3, 1.2); }
@keyframes bpEvict { 0% { transform: none; opacity: 1; } 30% { transform: translateY(-8px) rotate(-6deg); } 100% { transform: translate(-30px, 40px) rotate(-24deg) scale(.7); opacity: 0; } }
.bp-card.bp-evicting { border-color: var(--coral); background: var(--coral-soft); animation: bpEvict .36s cubic-bezier(.5, 0, .75, 0) forwards; }
@keyframes bpShake { 0%, 100% { transform: none; } 25% { transform: translateX(-5px); } 50% { transform: translateX(5px); } 75% { transform: translateX(-3px); } }
.bp-slots.bp-shake { animation: bpShake .35s; }

.bp-queue { display: flex; gap: 4px; margin-top: 14px; overflow-x: auto; scrollbar-width: none; }
.bp-queue:empty { display: none; }
.bp-chip { flex: 0 0 auto; padding: 3px 7px; border-radius: 99px; color: var(--muted); background: var(--surface); font-family: var(--mono); font-size: 10.5px; transition: .2s; }
.bp-chip.now { color: #fff; background: var(--blue); transform: scale(1.15); }
.bp-chip.hit { color: var(--green-deep); background: var(--lime); }
.bp-chip.miss { color: #fff; background: var(--coral); }

.bp-rate { display: flex; align-items: center; gap: 10px; margin-top: 6px; }
.bp-rate svg { width: 38px; height: 38px; transform: rotate(-90deg); }
.bp-rate circle { fill: none; stroke-width: 4; }
.bp-rate .bg { stroke: var(--surface-soft); }
.bp-rate .fg { stroke: var(--green); stroke-linecap: round; stroke-dasharray: 100; stroke-dashoffset: 100; transition: stroke-dashoffset .6s cubic-bezier(.2, .8, .3, 1); }
.bp-rate strong { margin: 0; }

.bp-ledger-wrap { display: grid; gap: 7px; }
.bp-ledger { display: flex; gap: 2px; height: 18px; padding: 3px; border-radius: 8px; background: var(--surface-soft); overflow: hidden; }
.bp-ledger:empty { height: auto; min-height: 18px; }
.bp-ledger:empty::before { content: "each lookup adds a block: wide coral = disk read, thin green = buffer hit"; align-self: center; padding-left: 6px; color: var(--muted); font-size: 10.5px; }
.bp-ledger i { min-width: 3px; border-radius: 4px; transform-origin: left; animation: bpGrow .4s cubic-bezier(.2, .8, .3, 1.2); }
.bp-ledger i.miss { background: var(--coral); }
.bp-ledger i.hit { background: var(--green); }
@keyframes bpGrow { from { transform: scaleX(0); } }

/* Production drill: read heads over index and heap pages. */
.st-watch { flex: 0 0 auto; white-space: nowrap; font-family: var(--mono); font-size: 11px; color: var(--muted); }
.st-watch b { color: var(--ink); font-size: 13px; }
.st-strips { position: relative; display: grid; gap: 6px; padding-top: 18px; }
.st-strip-label { color: var(--muted); font-size: 10px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase; }
.st-strip { display: grid; gap: 4px; }
.st-strip.index { grid-template-columns: repeat(8, minmax(0, 1fr)); margin-bottom: 20px; }
.st-strip.heap { grid-template-columns: repeat(10, minmax(0, 1fr)); row-gap: 22px; }
.st-cell { display: grid; place-items: center; height: 26px; border: 1px solid var(--line); border-radius: 5px; color: var(--muted); background: var(--surface); font-family: var(--mono); font-size: 9.5px; transition: background .2s, color .2s, border-color .2s; }
.st-strip.index .st-cell { border-color: var(--blue-soft); }
.st-cell.miss { border-color: var(--coral); color: #fff; background: var(--coral); }
.st-cell.good { border-color: var(--green); color: #fff; background: var(--green); }
.st-cell.hit { border-color: var(--green); color: var(--green-deep); background: var(--lime); }
@keyframes stPop { 0% { transform: scale(.7); } 50% { transform: scale(1.25); } 100% { transform: none; } }
.st-cell.st-pop { animation: stPop .35s cubic-bezier(.2, .8, .3, 1.4); }
.st-skip { display: none; }
.st-strips.skip-heap .st-strip.heap { opacity: .35; filter: grayscale(1); }
.st-strips.skip-heap .st-skip { display: block; position: absolute; bottom: 20px; left: 50%; width: max-content; max-width: 90%; padding: 5px 10px; border-radius: 99px; color: var(--green-deep); background: var(--green-soft); box-shadow: 0 0 0 1px var(--green); font-size: 11px; font-weight: 700; text-align: center; transform: translateX(-50%); }
.st-arcs { position: absolute; inset: 0; width: 100%; height: 100%; overflow: visible; pointer-events: none; }
.st-arcs path { fill: none; stroke-width: 1.8; stroke-linecap: round; opacity: .8; }
.st-arcs path.heap { stroke: var(--coral); }
.st-arcs path.covering { stroke: var(--green); }
.st-arcs path.hit { stroke: var(--green); stroke-dasharray: 3 3; }
.st-head { position: absolute; top: 0; left: 0; width: 14px; height: 12px; opacity: 0; background: var(--ink); clip-path: polygon(0 0, 100% 0, 50% 100%); transition: transform .28s cubic-bezier(.3, 1.5, .5, 1), opacity .2s; pointer-events: none; }
.st-head.on { opacity: 1; }

@media (max-width: 900px) {
  .st-anatomy, .bp-stage { grid-template-columns: 1fr; }
}
@media (max-width: 680px) {
  .bp-shelf { grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 5px; }
  .bp-card { padding: 7px 4px; }
  .bp-card small { font-size: 8.5px; }
  .st-divider { display: none; }
}