:root {
  --bg: #f8fafc;
  --header-bg: rgba(255, 255, 255, 0.8);
  --card: #ffffff;
  --accent: #0ea5e9;
  --accent-hover: #0284c7;
  --text: #0f172a;
  --muted: #64748b;
  --border: #e2e8f0;
  --radius: 12px;
  --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
  --safe-area-inset-top: env(safe-area-inset-top, 0px);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f172a;
    --header-bg: rgba(15, 23, 42, 0.9);
    --card: #1e293b;
    --text: #f8fafc;
    --muted: #94a3b8;
    --border: #334155;
    --input-bg: #1e293b;
  }
}

:root {
  --input-bg: #ffffff;
}

* {
  box-sizing: border-box;
  margin: 0; padding: 0;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  padding-bottom: 2rem;
}

/* STICKY HEADER */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--header-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: calc(1rem + var(--safe-area-inset-top)) 1rem 1rem;
}

.header-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.rx-grid {
  display: grid;
  grid-template-columns: 30px repeat(6, 1fr);
  gap: 4px;
  align-items: center;
}

.rx-label {
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  text-align: center;
}

.rx-row-label {
  font-weight: 800;
  color: var(--accent);
  font-size: 0.9rem;
}

.header input {
  width: 100%;
  padding: 8px 4px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--card);
  color: var(--text);
  font-size: 0.9rem;
  text-align: center;
  appearance: textfield;
}

/* ACCORDION */
.container {
  max-width: 600px;
  margin: 1.5rem auto;
  padding: 0 1rem;
}

.module {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 1rem;
  overflow: hidden;
  box-shadow: var(--shadow);
}

.module-header {
  padding: 1.25rem 1rem;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  min-height: 44px;
}

.module-title h2 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 2px;
}

.module-title p {
  font-size: 0.8rem;
  color: var(--muted);
}

.icon {
  width: 20px; height: 20px;
  transition: transform 0.3s ease;
  stroke: var(--muted);
}

.module.active .icon {
  transform: rotate(180deg);
  stroke: var(--accent);
}

/* CONTENT */
.module-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease-out, padding 0.3s ease;
  padding: 0 1rem;
}

.module.active .module-content {
  max-height: 2000px; /* high enough for any content */
  padding-bottom: 1.5rem;
}

.rx-grid {
  display: grid;
  grid-template-columns: 30px repeat(6, 1fr);
  gap: 4px;
  align-items: center;
}

.input-row {
  display: grid;
  grid-template-columns: 1fr 1fr; /* 2 columns on mobile for perfect alignment */
  gap: 12px;
  margin-top: 1rem;
}

@media (min-width: 600px) {
  .input-row {
    grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
  }
}

.input-field {
  width: 100%;
}

.input-field.wide {
  grid-column: span 2; /* Spans full width on 2-column mobile view */
}

@media (min-width: 600px) {
  .input-field.wide {
    grid-column: span 1; /* Fits back into the flow on desktop */
    min-width: 160px;
  }
}

label {
  display: block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--muted);
  margin-bottom: 4px;
}

input[type="number"], select {
  width: 100%;
  padding: 12px;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--input-bg);
  color: var(--text);
  font-size: 1rem;
  transition: border-color 0.2s, box-shadow 0.2s;
}

input:focus, select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(14, 165, 233, 0.2);
}

/* STEPPER CONTROLS */
.stepper {
  display: flex;
  align-items: stretch;
  background: var(--input-bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  overflow: hidden;
  height: 48px;
}

.stepper input {
  flex: 1;
  border: none !important;
  border-radius: 0 !important;
  text-align: center;
  padding: 0 4px !important;
  width: 50px !important; /* Min width for mobile */
  background: transparent !important;
  -moz-appearance: textfield;
}

.stepper input::-webkit-inner-spin-button,
.stepper input::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

.step-btn {
  background: var(--border);
  color: var(--text);
  border: none;
  width: 44px;
  font-size: 1.25rem;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.2s;
}

.step-btn:active {
  background: var(--accent);
  color: white;
}

/* INDEX PRESETS */
.index-select {
  margin-top: 4px;
  font-size: 0.8rem;
  background: var(--border);
  border-radius: 4px;
}

/* RESULT BOX */
.result-display {
  margin-top: 1.5rem;
  padding: 1rem;
  background: var(--accent);
  color: white;
  border-radius: 8px;
  text-align: center;
}

.result-val {
  font-size: 1.4rem;
  font-weight: 800;
  display: block;
}

.result-label {
  font-size: 0.75rem;
  opacity: 0.9;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* WORKINGS SECTION */
.workings {
  margin-top: 1rem;
  border-top: 1px dashed var(--border);
  padding-top: 1rem;
}

.workings summary {
  font-size: 0.75rem;
  color: var(--muted);
  cursor: pointer;
  list-style: none; /* Hide default arrow */
  display: flex;
  align-items: center;
  gap: 4px;
}

.workings summary::before {
  content: "→";
  font-size: 10px;
}

.workings-content {
  margin-top: 8px;
  font-family: monospace;
  font-size: 0.8rem;
  color: var(--muted);
  background: var(--bg);
  padding: 8px;
  border-radius: 4px;
  white-space: pre-wrap;
}

/* SEGMENTED CONTROL */
.segmented-control {
  display: flex;
  background: var(--border);
  padding: 2px;
  border-radius: 8px;
  margin-bottom: 1.25rem;
}

.segment-btn {
  flex: 1;
  border: none;
  background: transparent;
  padding: 8px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--muted);
  cursor: pointer;
  border-radius: 6px;
  transition: all 0.2s;
}

.segment-btn.active {
  background: var(--accent);
  color: white;
  box-shadow: 0 1px 2px rgba(0,0,0,0.1);
}

.hidden {
  display: none !important;
}

/* UTILS */
.transpose-btn {
  background: var(--accent);
  color: white;
  border: none;
  border-radius: 4px;
  padding: 4px 8px;
  font-size: 0.7rem;
  font-weight: 700;
  cursor: pointer;
}

.warning {
  background: #fffbeb;
  border: 1px solid #fef3c7;
  color: #92400e;
  padding: 10px;
  border-radius: 6px;
  font-size: 0.8rem;
  margin-top: 10px;
}

@media (max-width: 480px) {
  .rx-grid {
    font-size: 0.8rem;
  }
}