/* ==========================================================================
   CALCULATOR — the product. White form panel + black results panel.
   Sits inside the hero band, above the fold.
   ========================================================================== */

.calc__shell {
  display: grid;
  grid-template-columns: 1fr;
  border: var(--bw-strong) solid var(--border);
  box-shadow: var(--shadow-lg);
  background: var(--white);
  /* The hero sets white text; the card must reassert its own colour or every
     black-on-white label inside it renders invisible. */
  color: var(--fg);
  text-align: left;
}

/* Grid children default to min-width:auto and would otherwise refuse to
   shrink below their content, pushing the page sideways on narrow phones. */
.calc__shell > * {
  min-width: 0;
}

@media (min-width: 900px) {
  .calc__shell {
    grid-template-columns: 1.5fr 1fr;
  }
}

/* --- Form side ------------------------------------------------------------ */

.calc__form {
  padding: var(--s6);
}

@media (min-width: 640px) {
  .calc__form {
    padding: 32px;
  }
}

.calc__legend {
  display: flex;
  align-items: center;
  gap: var(--s3);
  margin-bottom: var(--s4);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.2em;
}

.calc__legend::before {
  content: "";
  flex: 0 0 auto;
  width: 14px;
  height: 14px;
  background: var(--red);
  border: 2px solid var(--border);
}

.calc__form fieldset {
  margin: 0 0 var(--s6);
  padding: 0;
  border: 0;
}

.calc__form legend,
.field > label,
.calc__sublabel {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.16em;
}

.calc__form legend {
  margin-bottom: var(--s3);
  padding: 0;
}

/* --- Mode tabs -----------------------------------------------------------
   The black container plus a 2px gap draws the dividing rules for us, so the
   grid can reflow to any column count without edge-case border rules. */

.calc__modes {
  display: grid;
  gap: 2px;
  grid-template-columns: repeat(2, 1fr);
  background: var(--border);
  border: var(--bw) solid var(--border);
  box-shadow: var(--shadow-sm);
}

/* Five tabs never fill a 2- or 3-column grid evenly, and the leftover cell
   would show the container's black backing. The last tab takes the slack. */
.calc__mode:last-child {
  grid-column: span 2;
}

@media (min-width: 520px) {
  .calc__modes {
    grid-template-columns: repeat(3, 1fr);
  }
}

@media (min-width: 900px) {
  .calc__modes {
    grid-template-columns: repeat(5, 1fr);
  }
  .calc__mode:last-child {
    grid-column: auto;
  }
}

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

.calc__mode span {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--s2);
  height: 100%;
  padding: var(--s3) var(--s2);
  background: var(--white);
  font-size: 0.6875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  text-align: center;
  cursor: pointer;
  transition: background-color var(--dur) var(--ease);
}

.calc__mode input:checked + span {
  background: var(--blue);
  color: var(--white);
}

.calc__mode input:focus-visible + span {
  outline: var(--bw-strong) solid var(--red);
  outline-offset: -4px;
}

/* Each mode is labelled by its own geometric glyph. */
.calc__mode span::before {
  content: "";
  flex: 0 0 auto;
  width: 12px;
  height: 12px;
  border: 2px solid currentColor;
}

.calc__mode--circle span::before {
  border-radius: 9999px;
}

.calc__mode--lshape span::before {
  clip-path: polygon(0 0, 55% 0, 55% 45%, 100% 45%, 100% 100%, 0 100%);
  background: currentColor;
  border: 0;
}

.calc__mode--area span::before {
  height: 8px;
}

.calc__mode--volume span::before {
  transform: rotate(45deg);
}

/* --- Fields --------------------------------------------------------------- */

.calc__row {
  display: grid;
  gap: var(--s4);
  grid-template-columns: 1fr;
}

@media (min-width: 480px) {
  .calc__row--2 {
    grid-template-columns: repeat(2, 1fr);
  }
}

.field {
  display: flex;
  flex-direction: column;
  gap: var(--s2);
}

.field__control {
  display: flex;
  border: var(--bw) solid var(--border);
  box-shadow: var(--shadow-sm);
  background: var(--white);
}

.field__control:focus-within {
  outline: var(--bw-strong) solid var(--blue);
  outline-offset: 2px;
}

.field input,
.field select {
  width: 100%;
  min-width: 0;
  padding: var(--s3) var(--s4);
  border: 0;
  border-radius: 0;
  background: transparent;
  font-family: inherit;
  font-size: 1.0625rem;
  font-weight: 700;
  color: inherit;
}

.field input:focus,
.field select:focus {
  outline: none;
}

.field input[type="number"] {
  -moz-appearance: textfield;
  appearance: textfield;
}

.field input[type="number"]::-webkit-outer-spin-button,
.field input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

/* Unit select attached to the right of the input. */
.field__unit {
  flex: 0 0 auto;
  display: flex;
  align-items: center;
  padding-inline: var(--s2);
  border-left: var(--bw) solid var(--border);
  background: var(--muted);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.field__unit--pre {
  border-left: 0;
  border-right: var(--bw) solid var(--border);
}

.field__unit select {
  padding: var(--s2) var(--s1);
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  cursor: pointer;
}

.field__hint {
  font-size: 0.8125rem;
  font-weight: 500;
  line-height: 1.4;
  margin: 0;
}

.calc__pair-label {
  margin: 0 0 var(--s2);
  font-size: 0.6875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--blue);
}

.calc__pair + .calc__pair {
  margin-top: var(--s4);
}

/* --- "What to measure" figure -------------------------------------------- */

.diagram {
  margin-top: var(--s4);
  padding: var(--s3);
  background: var(--muted);
  border: var(--bw) solid var(--border);
  box-shadow: var(--shadow-sm);
}

.diagram svg {
  display: block;
  width: 100%;
  max-width: 340px;
  height: auto;
  margin-inline: auto;
}

.diagram__t {
  font-family: inherit;
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0.06em;
  fill: var(--fg);
}

.diagram__t--light {
  fill: var(--white);
}

/* --- Waste slider --------------------------------------------------------- */

.calc__waste-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s4);
  margin-bottom: var(--s2);
}

.calc__waste-value {
  padding: 2px var(--s3);
  background: var(--yellow);
  border: 2px solid var(--border);
  font-size: 0.875rem;
  font-weight: 900;
}

input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 24px;
  margin: 0;
  background: transparent;
  cursor: pointer;
}

input[type="range"]::-webkit-slider-runnable-track {
  height: 12px;
  background: var(--white);
  border: 2px solid var(--border);
}

input[type="range"]::-moz-range-track {
  height: 12px;
  background: var(--white);
  border: 2px solid var(--border);
}

/* Square thumb — no rounded corners anywhere in this system. */
input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 22px;
  height: 22px;
  margin-top: -7px;
  background: var(--red);
  border: 2px solid var(--border);
}

input[type="range"]::-moz-range-thumb {
  width: 18px;
  height: 18px;
  border-radius: 0;
  background: var(--red);
  border: 2px solid var(--border);
}

input[type="range"]:focus-visible {
  outline: var(--bw-strong) solid var(--blue);
  outline-offset: 4px;
}

/* --- Moisture toggle ------------------------------------------------------ */

.calc__toggle {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2px;
  background: var(--border);
  border: var(--bw) solid var(--border);
  box-shadow: var(--shadow-sm);
}

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

.calc__toggle span {
  display: block;
  padding: var(--s2) var(--s3);
  background: var(--white);
  font-size: 0.6875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  text-align: center;
  cursor: pointer;
}

.calc__toggle input:checked + span {
  background: var(--yellow);
}

.calc__toggle input:focus-visible + span {
  outline: var(--bw-strong) solid var(--blue);
  outline-offset: -4px;
}

.calc__actions {
  display: flex;
  flex-wrap: wrap;
  gap: var(--s3);
  margin-top: var(--s6);
}

.calc__error {
  margin: var(--s4) 0 0;
  padding: var(--s3) var(--s4);
  background: var(--red);
  color: var(--white);
  border: var(--bw) solid var(--border);
  font-size: 0.9375rem;
  font-weight: 700;
}

.calc__error:empty {
  display: none;
}

/* --- Results side: black panel ------------------------------------------- */

.calc__results {
  padding: var(--s6);
  background: var(--fg);
  color: var(--white);
  border-top: var(--bw-strong) solid var(--border);
}

@media (min-width: 640px) {
  .calc__results {
    padding: 32px;
  }
}

@media (min-width: 900px) {
  .calc__results {
    border-top: 0;
    border-left: var(--bw-strong) solid var(--border);
  }
}

/* A <p>, not a heading — it must not appear in the page's heading outline. */
.calc__results-title {
  margin: 0 0 var(--s4);
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--yellow);
}

/* Headline figure — the answer people came for. */
.result-hero {
  padding: var(--s4) var(--s6);
  margin-bottom: var(--s4);
  background: var(--yellow);
  color: var(--fg);
  border: var(--bw) solid var(--border);
}

.result-hero__label {
  margin: 0;
  font-size: 0.6875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.2em;
}

.result-hero__value {
  margin: var(--s1) 0 0;
  font-size: clamp(2.5rem, 8vw, 3.25rem);
  font-weight: 900;
  line-height: 0.9;
  letter-spacing: -0.04em;
}

.result-hero__unit {
  font-size: 0.9375rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}

.result-list {
  display: grid;
  gap: var(--s2);
  margin: 0 0 var(--s4);
  padding: 0;
}

/* [hidden] must beat the flex display below. */
.result-list div[hidden] {
  display: none;
}

.result-list div {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: var(--s3);
  padding-bottom: var(--s2);
  border-bottom: 2px solid rgba(255, 255, 255, 0.25);
}

.result-list dt {
  font-size: 0.6875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--muted);
}

.result-list dd {
  margin: 0;
  font-size: 1.125rem;
  font-weight: 900;
  letter-spacing: -0.02em;
  text-align: right;
}

.result-note {
  display: flex;
  gap: var(--s3);
  margin: 0;
  font-size: 0.8125rem;
  line-height: 1.5;
  color: var(--muted);
}

.result-note + .result-note {
  margin-top: var(--s3);
}

.result-note::before {
  content: "";
  flex: 0 0 auto;
  width: 12px;
  height: 12px;
  margin-top: 5px;
  background: var(--blue);
  clip-path: polygon(50% 0%, 0% 100%, 100% 100%);
}

.result-note--waste::before {
  background: var(--yellow);
}