/* =========================================================
   BINTAN 200MW AI DATA CENTER
   Version B - Engineering Blueprint
   base.css : tokens, layout engine, nav, footer, primitives
   ========================================================= */

/* ---------- TOKENS ---------- */
:root {
  --bg: #F5F2EC;
  --paper: #FBF9F5;
  --ink: #1A1A1A;
  --ink-2: #3A3A38;
  --ink-3: #6B6A65;
  --blue: #1E3A5F;
  --blue-2: #2F5583;
  --blue-wash: #E6EBF1;
  --blue-hover: #16304F;
  --red: #C0392B;
  --red-hover: #9F2F22;
  --yellow: #F1C40F;
  --yellow-ink: #C9A400;
  --yellow-wash: #FBF6DC;
  --white: #FFFFFF;
  --skeleton: #E4E0D6;
  --skeleton-hi: #EFEBE1;
  --viewer-bg: #C6CBD0;

  --line: rgba(30, 58, 95, 0.22);
  --line-soft: rgba(30, 58, 95, 0.12);
  --rule: rgba(26, 26, 26, 0.14);

  --grid-cell: 32px;

  --font-head: "Archivo", "Segoe UI", system-ui, sans-serif;
  --font-body: "Source Serif 4", Georgia, "Times New Roman", serif;
  --font-mono: "Roboto Mono", "Consolas", "Courier New", monospace;

  --s1: 0.5rem;
  --s2: 1rem;
  --s3: 1.5rem;
  --s4: 2rem;
  --s5: 3rem;
  --section: clamp(3rem, 8vw, 6rem);

  --nav-h: 75px;
  --measure: 72ch;
  --wrap: 72rem;
  --gutter: clamp(1rem, 4vw, 2.5rem);
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* ---------- RESET ---------- */
*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
[id] { scroll-margin-top: calc(var(--nav-h) + 1rem); }

body {
  margin: 0;
  background-color: var(--bg);
  background-image:
    repeating-linear-gradient(to right, rgba(30, 58, 95, 0.055) 0 1px, transparent 1px var(--grid-cell)),
    repeating-linear-gradient(to bottom, rgba(30, 58, 95, 0.055) 0 1px, transparent 1px var(--grid-cell));
  color: var(--ink);
  font-family: var(--font-body);
  font-size: clamp(1rem, 1.5vw, 1.125rem);
  line-height: 1.68;
  font-weight: 400;
  padding-top: var(--nav-h);
  overflow-wrap: anywhere;
}

img, svg { max-width: 100%; }
svg { display: block; }

h1, h2, h3, h4, h5 {
  font-family: var(--font-head);
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 0.5em;
  min-height: 1lh;
}

p { margin: 0 0 1em; min-height: 1lh; }
ul, ol { margin: 0 0 1em; padding-left: 1.25em; }
li { margin-bottom: 0.4em; }
a { color: var(--blue); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--red); }
strong { font-weight: 600; color: var(--ink); }
small { font-size: 0.875rem; }

/* ---------- SKIP LINK ---------- */
.skip-link {
  position: absolute;
  left: 1rem;
  top: -4rem;
  z-index: 200;
  padding: 0.6rem 1rem;
  background: var(--blue);
  color: var(--white);
  font-family: var(--font-mono);
  font-size: 0.875rem;
  text-decoration: none;
}
.skip-link:focus { top: 0.75rem; color: var(--white); }

/* =========================================================
   PAGE LAYOUT ENGINE - CSS GRID ONLY
   ========================================================= */
.page-layout {
  display: grid;
  grid-template-columns:
    [full-start] minmax(var(--gutter), 1fr)
    [content-start] min(var(--wrap), calc(100% - (var(--gutter) * 2)))
    [content-end] minmax(var(--gutter), 1fr)
    [full-end];
  row-gap: 0;
}
.page-layout > * { grid-column: content; min-width: 0; }
.page-layout > .full-bleed { grid-column: full; }

/* Sections stack with vertical rhythm */
.section { padding-block: var(--section); min-width: 0; }

.stack { display: flex; flex-direction: column; gap: var(--s3); min-width: 0; }

/* =========================================================
   TYPOGRAPHY PRIMITIVES
   ========================================================= */
.kicker {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--blue);
  font-weight: 500;
  margin: 0 0 var(--s2);
  display: block;
}

h1.display {
  font-size: clamp(2rem, 5vw, 4rem);
  line-height: 1.08;
  letter-spacing: -0.02em;
}

h2.h2 {
  font-size: clamp(1.6rem, 3.4vw, 2.6rem);
  line-height: 1.14;
}

h3.h3 { font-size: clamp(1.2rem, 2vw, 1.5rem); line-height: 1.2; }

.lead {
  font-size: clamp(1.05rem, 1.7vw, 1.3rem);
  line-height: 1.55;
  color: var(--ink-2);
  max-width: var(--measure);
}

.body { max-width: var(--measure); color: var(--ink-2); }

.mono {
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  letter-spacing: 0.01em;
}

.label {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-3);
}

.section-head { margin-bottom: var(--s4); }
.section-head .h2 { margin-bottom: var(--s2); }

/* =========================================================
   NAV
   ========================================================= */
.topnav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  height: var(--nav-h);
  background: rgba(245, 242, 236, 0.94);
  backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--line);
  transition: transform 0.45s var(--ease);
}
.topnav.is-hidden {
  transform: translateY(-100%);
}
.topnav__inner {
  height: 100%;
  width: min(var(--wrap), calc(100% - (var(--gutter) * 2)));
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: var(--s3);
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--ink);
  flex: 0 0 auto;
}
.brand:hover { color: var(--ink); }
.brand__mark { width: 30px; height: 30px; flex: 0 0 auto; }
.brand__text {
  font-family: var(--font-head);
  font-weight: 700;
  font-size: 0.95rem;
  letter-spacing: 0.02em;
  line-height: 1;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.brand__text span {
  font-family: var(--font-mono);
  font-weight: 400;
  font-size: 0.875rem;
  letter-spacing: 0.12em;
  color: var(--ink-3);
}

.nav { margin-left: auto; }
.nav ul {
  display: flex;
  align-items: center;
  gap: clamp(0.5rem, 1.4vw, 1rem);
  list-style: none;
  margin: 0;
  padding: 0;
}
.nav li { margin: 0; display: flex; align-items: center; }
/* Separators are decorative, so they live in CSS instead of the list markup */
.nav li + li::before {
  content: "|";
  content: "|" / "";
  color: var(--line);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: 0 0.25rem;
  margin-right: clamp(0.5rem, 1.4vw, 1rem);
}
.nav a {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  letter-spacing: 0.02em;
  text-decoration: none;
  color: var(--ink-2);
  padding: 0.35rem 0.15rem;
  border-bottom: 2px solid transparent;
  white-space: nowrap;
}
.nav a:hover { color: var(--blue); border-bottom-color: var(--line); }
.nav a[aria-current="page"] { color: var(--blue); border-bottom-color: var(--red); }

.navtoggle {
  display: none;
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  background: var(--paper);
  border: 1px solid var(--line);
  color: var(--blue);
  padding: 0.4rem 0.7rem;
  cursor: pointer;
}
.navtoggle:hover { border-color: var(--blue); }

@media (max-width: 1024px) {
  .navtoggle { display: block; }
  .nav {
    position: absolute;
    top: var(--nav-h);
    left: 0; right: 0;
    margin: 0;
    background: var(--paper);
    border-bottom: 1px solid var(--line);
    max-height: 0;
    overflow: hidden;
    visibility: hidden;
    transition: max-height 0.25s ease, visibility 0s linear 0.25s;
  }
  .nav.is-open {
    max-height: 26rem;
    overflow: auto;
    visibility: visible;
    transition: max-height 0.25s ease, visibility 0s;
  }
  .nav ul {
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 0.5rem 1rem 1rem;
  }
  .nav li { display: block; }
  .nav li + li::before { content: none; }
  .nav a {
    padding: 0.7rem 0.25rem;
    border-bottom: 1px solid var(--line-soft);
    font-size: 0.875rem;
  }
}

/* =========================================================
   FULL-BLEED BANDS
   ========================================================= */
.band {
  background: var(--paper);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
}
.band--blue {
  background: var(--blue-wash);
  color: var(--ink);
  border-color: var(--blue);
  border-top-width: 2px;
  border-bottom-width: 2px;
}
.band--blue .kicker,
.band--blue .label { color: var(--blue); }
.band--blue h1, .band--blue h2, .band--blue h3 { color: var(--blue); }
.band--blue a { color: var(--blue); }
.band--blue .metric { background: var(--paper); }
.band--blue .deflist { border-color: var(--line); }
.band-inner {
  width: min(var(--wrap), calc(100% - (var(--gutter) * 2)));
  margin-inline: auto;
}
.band-inner--offset {
  padding-inline: clamp(1.5rem, 4vw, 3rem);
}

/* =========================================================
   BUTTONS - square, no radius
   ========================================================= */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  text-decoration: none;
  padding: 0.85rem 1.4rem;
  border: 1px solid var(--blue);
  background: var(--blue);
  color: var(--white);
  cursor: pointer;
  transition: background-color 0.18s ease, color 0.18s ease, border-color 0.18s ease;
}
.btn:hover { background: var(--blue-hover); color: var(--white); border-color: var(--blue-hover); }
.btn--ghost { background: transparent; color: var(--blue); }
.btn--ghost:hover { background: var(--blue-wash); color: var(--blue); }
.btn--red { background: var(--red); border-color: var(--red); }
.btn--red:hover { background: var(--red-hover); border-color: var(--red-hover); }
.btn--sm { padding: 0.55rem 0.9rem; font-size: 0.875rem; }

.btnrow { display: flex; flex-wrap: wrap; gap: var(--s2); align-items: center; }
.btnrow--between { justify-content: space-between; }

/* =========================================================
   METRIC / STAT PRIMITIVES
   ========================================================= */
.metrics {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
}

.metrics--2 { grid-template-columns: repeat(2, 1fr); }
.metric {
  background: var(--paper);
  padding: clamp(1.25rem, 3vw, 2rem);
  min-width: 0;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.metric__num {
  font-family: var(--font-mono);
  font-weight: 700;
  font-size: clamp(1.5rem, 4vw, 3rem);
  line-height: 1;
  color: var(--blue);
  letter-spacing: -0.02em;
}
.metric__num .unit { font-size: 0.5em; color: var(--ink-3); margin-left: 0.15em; }
.metric__label {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink);
}
.metric__note { font-size: 0.9375rem; color: var(--ink-3); line-height: 1.5; margin: 0; }
.metric--accent .metric__num { color: var(--red); }
.metrics--flush { border: 0; }
.metrics--rule-bottom { border-top: 0; border-left: 0; border-right: 0; }

@media (max-width: 760px) {
  .metrics { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 560px) {
  .metrics, .metrics--2 { grid-template-columns: 1fr; }
}

/* ---------- SPEC TABLE ---------- */
.specsheet {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9375rem;
}
.specsheet caption {
  text-align: left;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-3);
  padding-bottom: 0.6rem;
}
.specsheet th, .specsheet td {
  text-align: left;
  padding: 0.7rem 0.6rem;
  border-bottom: 1px solid var(--line-soft);
  vertical-align: top;
}
.specsheet thead th {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--blue);
  border-bottom: 1px solid var(--line);
}
.specsheet tbody th { font-weight: 600; color: var(--ink); }
.specsheet td.num, .specsheet th.num { font-family: var(--font-mono); white-space: nowrap; }
.specsheet tbody tr:hover { background: var(--blue-wash); }
.tablewrap { overflow-x: auto; border: 1px solid var(--line); }

/* ---------- CARDS ---------- */
.cardgrid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--s3);
}
.cardgrid--2 { grid-template-columns: repeat(2, 1fr); }
.cardgrid--4 { grid-template-columns: repeat(4, 1fr); }
.card {
  border: 1px solid var(--line);
  background: var(--paper);
  padding: clamp(1.1rem, 2.5vw, 1.6rem);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
  min-width: 0;
}
.card--roomy { gap: 0.75rem; }
.card__tag {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--red);
}
.card h3 { margin: 0; font-size: 1.15rem; }
.card p { margin: 0; font-size: 0.9688rem; color: var(--ink-2); }
.card__rule { height: 1px; background: var(--line-soft); margin: 0.2rem 0; }
@media (max-width: 900px) { .cardgrid, .cardgrid--4 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 560px) { .cardgrid, .cardgrid--2, .cardgrid--4 { grid-template-columns: 1fr; } }

/* ---------- CALLOUT (square, no left color bar cliche) ---------- */
.callout {
  border: 1px solid var(--line);
  background: var(--blue-wash);
  padding: clamp(1rem, 2.5vw, 1.5rem);
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}
.callout .label { color: var(--blue); }
.callout p { margin: 0; }

.pullquote {
  border-top: 2px solid var(--ink);
  border-bottom: 2px solid var(--ink);
  padding: var(--s3) 0;
  font-family: var(--font-head);
  font-size: clamp(1.25rem, 2.6vw, 1.9rem);
  line-height: 1.25;
  color: var(--ink);
  max-width: 40ch;
}

/* ---------- LISTS ---------- */
.deflist { display: flex; flex-direction: column; gap: 0; border-top: 1px solid var(--line); }
.deflist__row {
  display: grid;
  grid-template-columns: minmax(9rem, 14rem) 1fr;
  gap: var(--s3);
  padding: 0.9rem 0;
  border-bottom: 1px solid var(--line-soft);
  align-items: baseline;
}
.deflist__row dt { font-family: var(--font-mono); font-size: 0.875rem; text-transform: uppercase; letter-spacing: 0.05em; color: var(--blue); }
.deflist__row dd { margin: 0; }
@media (max-width: 560px) { .deflist__row { grid-template-columns: 1fr; gap: 0.5rem; } }

/* =========================================================
   FIGURE / DIAGRAM FRAME
   ========================================================= */
.figure {
  padding: 1.5rem;
  min-width: 0;
  overflow: visible;
}
.figure svg { width: 100%; height: auto; overflow: visible; }
.figcaption {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  color: var(--ink-3);
  letter-spacing: 0.02em;
  margin-top: 0.75rem;
  display: flex;
  gap: 0.5rem;
  align-items: baseline;
  flex-wrap: wrap;
}
.figcaption b { color: var(--red); font-weight: 500; }
/* Figure variants */
.figure--full {
  margin-left: calc(-1 * var(--gutter));
  margin-right: calc(-1 * var(--gutter));
  border-radius: 0;
}
@media (max-width: 760px) { .figure--full { margin-left: -1rem; margin-right: -1rem; } }

/* Soft horizontal rule */
.rule { display: block; border: none; border-top: 1px solid var(--rule); margin: 2.5rem 0; }
.rule--soft { border-color: var(--line-soft); margin-top: 2rem; margin-bottom: 2rem; }

/* Drawing utilities for hand-drawn SVG */
.ink { stroke: var(--ink); stroke-width: 1.4; fill: none; stroke-linecap: round; stroke-linejoin: round; }
.ink--blue { stroke: var(--blue); }
.ink--red { stroke: var(--red); }
.ink--yellow { stroke: var(--yellow-ink); }
.ink--thin { stroke-width: 1; }
.ink--thick { stroke-width: 2.4; }
.ink--dashed { stroke-dasharray: 6 5; }

.fill-paper { fill: var(--paper); }
.fill-bluewash { fill: var(--blue-wash); }

.svg-mono { font-family: var(--font-mono); fill: var(--blue); font-size: 0.9375rem; letter-spacing: 0.03em; pointer-events: none; }

.svg-mono--red { fill: var(--red); }
.svg-mono--light { fill: var(--white); }
.svg-mono--big { font-size: 1.5rem; font-weight: 700; letter-spacing: 0; }
.svg-mono--sm { font-size: 0.875rem; letter-spacing: 0.02em; }
.wobble { filter: url(#rough); }

/* Timeline milestone icons */
.tl-icon__ring { fill: var(--bg); stroke: var(--blue); stroke-width: 2.4; }
.tl-icon__tick { fill: none; stroke: var(--blue); stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.is-key .tl-icon__ring { stroke: var(--red); stroke-width: 3; }
.is-key .tl-icon__tick { stroke: var(--red); stroke-width: 2.4; }
.tl-icon__ring--future { stroke: var(--yellow-ink); stroke-dasharray: 5 4; }

/* =========================================================
   REVEAL (IntersectionObserver + CSS)
   The `js` class is set in <head>, so hidden-then-shown never flashes.
   `reveal-ready` is set by site.js; without it content stays visible.
   ========================================================= */
.js.reveal-ready [data-animate] {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s var(--ease), transform 0.6s var(--ease);
}
.js.reveal-ready [data-animate].is-visible {
  opacity: 1;
  transform: none;
}

/* =========================================================
   FOOTER
   ========================================================= */
.sitefoot {
  margin-top: var(--section);
  background: var(--paper);
  color: var(--ink-2);
  border-top: 2px solid var(--blue);
}
.sitefoot__inner {
  width: min(var(--wrap), calc(100% - (var(--gutter) * 2)));
  margin: 0 auto;
  padding: clamp(2.5rem, 5vw, 4rem) 0 2rem;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr;
  gap: var(--s4);
}
.sitefoot h3 {
  color: var(--blue);
  font-size: 1.05rem;
  margin-bottom: 0.75rem;
  font-family: var(--font-head);
}
.sitefoot p { color: var(--ink-3); font-size: 0.9375rem; }
.sitefoot a { color: var(--blue); text-decoration: none; }
.sitefoot a:hover { color: var(--red); text-decoration: underline; }
.sitefoot ul { list-style: none; padding: 0; margin: 0; }
.sitefoot li { margin-bottom: 0.4rem; font-size: 0.9375rem; }
.sitefoot__bottom {
  grid-column: 1 / -1;
  border-top: 1px solid var(--line);
  padding-top: 1.25rem;
  margin-top: var(--s2);
  display: flex;
  justify-content: space-between;
  gap: var(--s3);
  flex-wrap: wrap;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  letter-spacing: 0.03em;
  color: var(--ink-3);
}
@media (max-width: 760px) {
  .sitefoot__inner { grid-template-columns: 1fr; }
}

/* ---------- TOOLTIP FOR EMAIL DISPLAY ---------- */
[data-tooltip] {
  position: relative;
  cursor: pointer;
}
[data-tooltip]:hover::after,
[data-tooltip]:focus-visible::after {
  content: attr(data-tooltip);
  position: absolute;
  bottom: -2.5rem;
  left: 50%;
  transform: translateX(-50%);
  background: var(--ink);
  color: var(--paper);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  padding: 0.3rem 0.6rem;
  border-radius: 4px;
  white-space: nowrap;
  z-index: 10;
  pointer-events: none;
}
/* ---------- UTILITIES ---------- */

.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: var(--s4); align-items: start; }
.grid-2--wide-left { grid-template-columns: 1.4fr 1fr; }
.grid-2--wide-right { grid-template-columns: 1fr 1.4fr; }
@media (max-width: 760px) { .grid-2, .grid-2--wide-left, .grid-2--wide-right { grid-template-columns: 1fr; } }

.mt-1 { margin-top: var(--s1); }
.mt-2 { margin-top: var(--s2); }
.mt-4 { margin-top: var(--s4); }
.m-0 { margin: 0; }
.self-start { align-self: flex-start; }
.w-fit { width: fit-content; }
.w-full { width: 100%; }
.measure { max-width: var(--measure); }
.inset-l { padding-left: var(--s5); }
.rule--wide { margin-block: var(--s5); }

/* ---------- ACCESSIBILITY / REDUCED MOTION ---------- */
:focus-visible { outline: 2px solid var(--red); outline-offset: 2px; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .js.reveal-ready [data-animate] { opacity: 1; transform: none; }
  *, *::before, *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
}

/* ---------- BACK TO TOP BUTTON ---------- */
.back-to-top {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  width: 3.5rem;
  height: 3.5rem;
  border-radius: 50%;
  background: var(--red);
  color: var(--white);
  border: none;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  opacity: 0;
  visibility: hidden;
  transform: translateY(1rem);
  transition: opacity 0.3s ease, transform 0.3s ease, visibility 0.3s;
  z-index: 999;
  box-shadow: 0 4px 12px rgba(30, 58, 95, 0.25);
}
.back-to-top.is-visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}
.back-to-top:hover {
  background: var(--blue);
  transform: translateY(-2px);
}
.back-to-top svg {
  width: 1.5rem;
  height: 1.5rem;
  fill: currentColor;
}
.back-to-top .tooltip {
  position: absolute;
  right: 100%;
  top: 50%;
  transform: translateY(-50%) translateX(0.5rem);
  background: var(--ink);
  color: var(--white);
  padding: 0.5rem 0.75rem;
  border-radius: 0.25rem;
  font-size: 0.875rem;
  white-space: nowrap;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.2s ease, visibility 0.2s;
}
.back-to-top:hover .tooltip,
.back-to-top:focus-visible .tooltip {
  opacity: 1;
  visibility: visible;
}
@media (max-width: 560px) {
  .back-to-top {
    bottom: 1.5rem;
    right: 1.5rem;
    width: 3rem;
    height: 3rem;
  }
  .back-to-top .tooltip { display: none; }
}