:root {
  --bg: #eef1eb;
  --paper: #fffef8;
  --tape: #f3f0e4;
  --ink: #1f2a24;
  --muted: #5c6b63;
  --accent: #1a6b4f;
  --accent-soft: #d8ece4;
  --border: #c8d3cb;
  --error: #b42318;
  --shadow: 0 10px 30px rgba(26, 58, 47, 0.08);
  --mono: "Consolas", "Courier New", monospace;
  --sans: "Segoe UI", system-ui, sans-serif;
  --desktop-min: 1024px;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  overflow-x: clip;
  font-family: var(--sans);
  color: var(--ink);
  background:
    radial-gradient(circle at top left, #dfece4 0, transparent 40%),
    var(--bg);
  padding:
    env(safe-area-inset-top)
    env(safe-area-inset-right)
    env(safe-area-inset-bottom)
    env(safe-area-inset-left);
}

.app {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  max-width: none;
  min-height: auto;
  margin: 0 auto;
  padding: 0.75rem;
}

.panel {
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 12px;
  box-shadow: 0 4px 16px rgba(26, 58, 47, 0.06);
}

.calculator {
  order: 1;
  min-width: 0;
  padding: 1rem 1rem 1.25rem;
}

.tape-panel {
  order: 2;
  display: flex;
  flex-direction: column;
  min-height: 0;
  background: var(--tape);
}

.header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  margin-bottom: 0.75rem;
}

h1,
h2 {
  margin: 0;
  font-weight: 650;
}

h1 {
  font-size: 1.35rem;
}

h2 {
  font-size: 1.05rem;
}

.header-actions {
  position: relative;
  align-items: flex-start;
}

.fieldset {
  margin: 0;
  padding: 0;
  border: 0;
}

legend {
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 0.45rem;
}

.chip-group {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
}

.chip {
  display: inline-flex;
  cursor: pointer;
}

.chip input {
  position: absolute;
  opacity: 0;
  pointer-events: none;
}

.chip span {
  display: inline-flex;
  align-items: center;
  min-height: 44px;
  padding: 0.45rem 0.85rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  background: #fff;
  font-size: 0.92rem;
}

.chip input:checked + span {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
  font-weight: 600;
}

.sticky-controls {
  position: sticky;
  top: 0;
  z-index: 20;
  margin: 0 -1rem 1rem;
  padding: 0.5rem 1rem 0.85rem;
  background: var(--paper);
  border-bottom: 1px solid var(--border);
}

.input-section {
  margin-bottom: 0.85rem;
}

.input-section label {
  display: block;
  margin-bottom: 0.45rem;
  font-size: 0.9rem;
  color: var(--muted);
}

#amount {
  width: 100%;
  min-height: 48px;
  padding: 0.75rem 0.9rem;
  font: 600 1.75rem/1.2 var(--mono);
  border: 2px solid var(--border);
  border-radius: 10px;
  background: #fff;
}

#amount:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(26, 107, 79, 0.15);
}

.input-error {
  margin: 0.5rem 0 0;
  color: var(--error);
  font-size: 0.9rem;
}

.rate-section {
  margin-bottom: 0;
}

.custom-rate {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 0.75rem;
}

.custom-rate label {
  color: var(--muted);
}

#custom-rate {
  width: 100px;
  padding: 0.45rem 0.6rem;
  font: 600 1rem/1.2 var(--mono);
  border: 1px solid var(--border);
  border-radius: 8px;
}

.hidden {
  display: none !important;
}

.mobile-only {
  display: inline-flex;
}

.btn-icon {
  min-width: 44px;
  min-height: 44px;
  padding: 0.35rem 0.55rem;
  border: 1px solid var(--border);
  border-radius: 10px;
  background: #fff;
  font-size: 1.2rem;
  line-height: 1;
  cursor: pointer;
}

.settings-menu {
  position: absolute;
  top: calc(100% + 0.35rem);
  right: 0;
  z-index: 40;
  min-width: 200px;
  padding: 0.75rem;
  background: var(--paper);
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: var(--shadow);
}

.settings-menu[hidden] {
  display: none !important;
}

.settings-menu .btn-secondary {
  width: 100%;
  margin-top: 0.65rem;
  min-height: 44px;
}

.results {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
}

.scenario {
  min-width: 0;
  overflow-wrap: anywhere;
  padding: 0.85rem;
  border: 1px solid var(--border);
  border-radius: 12px;
  background: #fafcf9;
}

.scenario h2 {
  margin-bottom: 0.75rem;
  font-size: 0.98rem;
  color: var(--accent);
}

.equation {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.35rem;
  margin: 0 0 0.45rem;
  font-family: var(--mono);
  font-size: 0.95rem;
  word-break: break-word;
}

.equation.precise {
  color: var(--muted);
  font-size: 0.85rem;
  margin-bottom: 0.85rem;
}

.precise-desktop,
.values-main .precise-col {
  display: none;
}

.precise-details {
  margin: 0.5rem 0 0.75rem;
  padding: 0.35rem 0.5rem;
  border: 1px dashed var(--border);
  border-radius: 8px;
  background: #fff;
}

.precise-details summary {
  cursor: pointer;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--accent);
  padding: 0.25rem 0;
}

.eq-label {
  font-family: var(--sans);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
}

.values {
  width: 100%;
  table-layout: fixed;
  border-collapse: collapse;
  font-size: 0.88rem;
}

.values th,
.values td {
  padding: 0.35rem 0.4rem;
  text-align: left;
  border-top: 1px solid var(--border);
  overflow-wrap: anywhere;
}

.values thead th {
  font-size: 0.75rem;
  color: var(--muted);
  font-weight: 600;
  border-top: 0;
}

.values tbody th {
  font-weight: 600;
}

.values td:nth-child(2),
.values td:nth-child(3) {
  font-family: var(--mono);
}

.copy-actions {
  margin-top: 0.85rem;
  padding-top: 0.85rem;
  border-top: 1px dashed var(--border);
}

.copy-actions-tape {
  margin-top: 0.35rem;
  margin-bottom: 0.55rem;
  padding-top: 0;
  border-top: 0;
}

.copy-actions-label {
  display: block;
  margin-bottom: 0.45rem;
  font-size: 0.78rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.04em;
  color: var(--muted);
}

.copy-group {
  display: inline-flex;
  flex-wrap: wrap;
  gap: 0.3rem;
}

.copy-actions .copy-group,
.copy-actions-tape .copy-group {
  display: flex;
  flex-direction: column;
  flex-wrap: nowrap;
  gap: 0.35rem;
  width: 100%;
}

.copy-btn {
  min-height: 44px;
  padding: 0.35rem 0.65rem;
  border: 1px solid var(--border);
  border-radius: 7px;
  background: #fff;
  color: var(--ink);
  font: 600 0.85rem/1.2 var(--mono);
  cursor: pointer;
}

.copy-actions .copy-btn,
.copy-actions-tape .copy-btn {
  width: 100%;
  text-align: left;
}

.copy-actions-receipt {
  margin-top: 0.65rem;
  padding-top: 0.65rem;
}

.copy-btn-receipt {
  white-space: normal;
  line-height: 1.35;
  word-break: break-word;
}

.copy-btn-suffix {
  font-family: var(--sans);
  font-size: 0.72rem;
  font-weight: 600;
  color: var(--muted);
  margin-left: 0.2rem;
}

.copy-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.copy-btn.copied {
  background: var(--accent-soft);
  border-color: var(--accent);
  color: var(--accent);
}

.tape-details:not([open]) .tape,
.tape-details:not([open]) .tape-toolbar {
  display: none !important;
}

.tape-summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.85rem 1rem;
  cursor: pointer;
  font-weight: 650;
  list-style: none;
}

.tape-summary::-webkit-details-marker {
  display: none;
}

.tape-summary::after {
  content: '▾';
  color: var(--muted);
  font-size: 0.9rem;
}

.tape-details:not([open]) .tape-summary::after {
  content: '▸';
}

.tape-toolbar {
  display: flex;
  justify-content: flex-end;
  padding: 0 1rem 0.5rem;
  border-bottom: 1px dashed #bfb8a4;
}

.btn-secondary {
  padding: 0.35rem 0.7rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: #fff;
  cursor: pointer;
  font-size: 0.85rem;
}

.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.tape {
  overflow: auto;
  max-height: 40vh;
  padding: 0.5rem 1rem 1.25rem;
  font-family: var(--mono);
  font-size: 0.82rem;
  line-height: 1.45;
}

.tape-empty {
  margin: 0;
  color: var(--muted);
  font-family: var(--sans);
  font-size: 0.9rem;
}

.tape-line {
  padding: 0.55rem 0;
  border-bottom: 1px dotted #c9c0aa;
}

.tape-line header {
  font-weight: 700;
  margin-bottom: 0.2rem;
}

.tape-line p,
.tape-scenario {
  margin: 0.15rem 0;
}

/* --- Desktop (>= 1024px) --- */
@media (min-width: 1024px) {
  body {
    padding: 0;
  }

  .app {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 360px;
    gap: 1.25rem;
    max-width: 1240px;
    min-height: 100vh;
    padding: 1.5rem;
  }

  .panel {
    border-radius: 14px;
    box-shadow: var(--shadow);
  }

  .calculator {
    order: unset;
    padding: 1.5rem 1.75rem 2rem;
  }

  .tape-panel {
    order: unset;
    min-height: calc(100vh - 3rem);
  }

  .header {
    margin-bottom: 1.5rem;
  }

  h1 {
    font-size: 1.75rem;
  }

  .header-actions {
    display: flex;
    align-items: flex-start;
    gap: 0.75rem;
  }

  .mobile-only {
    display: none !important;
  }

  .settings-menu {
    position: static;
    display: block !important;
    min-width: 0;
    padding: 0;
    border: 0;
    box-shadow: none;
    background: transparent;
  }

  .settings-menu .btn-secondary {
    display: none;
  }

  .sticky-controls {
    position: static;
    margin: 0 0 1.5rem;
    padding: 0;
    border-bottom: 0;
  }

  .input-section {
    margin-bottom: 1.25rem;
  }

  #amount {
    max-width: 320px;
    min-height: 0;
    font-size: 1.5rem;
  }

  .rate-section {
    margin-bottom: 1.5rem;
  }

  .chip span {
    min-height: 0;
    display: inline-block;
    padding: 0.35rem 0.75rem;
  }

  .results {
    grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
    gap: 1rem;
  }

  .scenario {
    padding: 1rem;
  }

  .precise-desktop {
    display: block;
  }

  .values-main .precise-col {
    display: table-cell;
  }

  .precise-details {
    display: none;
  }

  .copy-btn {
    min-height: 2rem;
  }

  .tape-details[open] .tape,
  .tape-details[open] .tape-toolbar {
    display: block;
  }

  .tape-details summary {
    list-style: none;
    pointer-events: none;
  }

  .tape-summary {
    padding: 1rem 1rem 0.75rem;
    cursor: default;
    border-bottom: 1px dashed #bfb8a4;
  }

  .tape-summary::after {
    display: none;
  }

  .tape-toolbar {
    padding: 0 1rem 0.75rem;
  }

  .tape {
    max-height: none;
    flex: 1;
    padding-top: 0.75rem;
  }
}