:root {
  --bg: #1a1a1f;
  --surface: #25252d;
  --surface-raised: #2d2d38;
  --border: #3a3a48;
  --border-light: #4a4a5a;
  --accent: #6a8fff;
  --accent-dim: #3a5fcc;
  --text: #e0e0e8;
  --text-dim: #9090a8;
  --text-header: #c0c8ff;
  --selected-bg: #2a3a6a;
  --selected-border: #6a8fff;
  --green: #6aff8f;
  --font-mono: "Courier New", Courier, monospace;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  background: url('bg.png') center center / cover fixed;
  color: var(--text);
  font-family: "Segoe UI", system-ui, sans-serif;
  font-size: 13px;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-height: 100vh;
  padding: 0 16px;
}

.ui-container {
  background: rgba(26, 26, 31, 0.95);
  padding: 16px;
  width: 100%;
  max-width: 860px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
}

h1 {
  font-size: 18px;
  font-weight: 600;
  color: var(--text-header);
  letter-spacing: 0.04em;
  margin-bottom: 14px;
  text-align: center;
}

/* ── Tabs ─────────────────────────────────────────────────────────────────── */

.tabs {
  display: flex;
  border-bottom: 1px solid var(--border);
  margin-bottom: 14px;
  width: 100%;
  max-width: 820px;
}

.tab-btn {
  background: none;
  border: none;
  border-bottom: 2px solid transparent;
  color: var(--text-dim);
  cursor: pointer;
  font-size: 13px;
  padding: 8px 18px;
  transition: color 0.15s, border-color 0.15s;
}

.tab-btn:hover {
  color: var(--text);
}

.tab-btn.active {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.tab-panel {
  display: none;
  width: 100%;
  max-width: 820px;
}

.tab-panel.active {
  display: block;
}

/* ── Section boxes (like tkinter LabelFrame) ─────────────────────────────── */

.section {
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 12px 14px 14px;
  position: relative;
  background: var(--surface);
}

.section legend,
.section-title {
  position: absolute;
  top: -9px;
  left: 10px;
  background: var(--surface);
  color: var(--text-dim);
  font-size: 11px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  padding: 0 5px;
}

/* ── Form rows ───────────────────────────────────────────────────────────── */

.form-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 10px;
}

.form-row label {
  width: 80px;
  color: var(--text-dim);
  flex-shrink: 0;
  font-size: 12px;
}

.form-row input {
  background: var(--surface-raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text);
  font-size: 13px;
  padding: 4px 8px;
  width: 140px;
  outline: none;
  transition: border-color 0.15s;
}

.form-row input:focus {
  border-color: var(--accent-dim);
}

.form-row select,
.form-row select::picker(select) {
  appearance: base-select;
}

.form-row select {
  background: var(--surface-raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text);
  font-size: 13px;
  padding: 4px 8px;
  width: 140px;
  outline: none;
  transition: border-color 0.15s;
  cursor: pointer;
}

.form-row select:focus,
.form-row select:open {
  border-color: var(--accent-dim);
}

.form-row select::picker-icon {
  color: var(--text-dim);
}

.form-row select::picker(select) {
  background: var(--surface-raised);
  border: 1px solid var(--accent-dim);
  border-radius: 4px;
  padding: 2px 0;
}

.form-row select option {
  background: var(--surface-raised);
  color: var(--text);
  font-size: 13px;
  padding: 4px 8px;
}

.form-row select option:hover,
.form-row select option:focus {
  background: var(--surface);
}

.form-row select option:checked {
  background: var(--selected-bg);
  color: var(--accent);
}

.form-row select option::checkmark {
  display: none;
}

/* Hide number input spinners */
.form-row input[type="number"]::-webkit-inner-spin-button,
.form-row input[type="number"]::-webkit-outer-spin-button {
  -webkit-appearance: none;
  margin: 0;
}
.form-row input[type="number"] {
  -moz-appearance: textfield;
}

/* ── Buttons ─────────────────────────────────────────────────────────────── */

.btn {
  background: var(--accent-dim);
  border: none;
  border-radius: 5px;
  color: #fff;
  cursor: pointer;
  font-size: 13px;
  font-weight: 600;
  padding: 7px 22px;
  transition: background 0.15s;
}

.btn:hover {
  background: var(--accent);
}

.btn:active {
  background: #2a4fbb;
}

/* ── Two-column grid used on Calculator and Sim tabs ─────────────────────── */

.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-bottom: 12px;
}

.grid-3 {
  display: grid;
  grid-template-columns: 1fr 1fr auto;
  gap: 12px;
  align-items: start;
  margin-bottom: 12px;
}

.btn-cell {
  display: flex;
  align-items: flex-end;
  padding-bottom: 2px;
}

/* ── Results table ────────────────────────────────────────────────────────── */

.table-wrap {
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 12px;
}

thead th {
  background: var(--surface-raised);
  color: var(--text-dim);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.05em;
  padding: 7px 10px;
  text-align: center;
  text-transform: uppercase;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
  position: sticky;
  top: 0;
  z-index: 1;
}

tbody td {
  border-bottom: 1px solid var(--border);
  padding: 6px 10px;
  text-align: center;
  white-space: nowrap;
}

tbody tr:last-child td {
  border-bottom: none;
}

tbody tr:hover {
  background: var(--surface-raised);
  cursor: pointer;
}

tbody tr.selected {
  background: var(--selected-bg);
  outline: 1px solid var(--selected-border);
}

.scrollable-table {
  max-height: 560px;
  overflow-y: auto;
}

.scrollable-table::-webkit-scrollbar {
  width: 6px;
}

.scrollable-table::-webkit-scrollbar-track {
  background: var(--surface);
}

.scrollable-table::-webkit-scrollbar-thumb {
  background: var(--border-light);
  border-radius: 3px;
}

/* ── Encoding tab ─────────────────────────────────────────────────────────── */

.enc-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-top: 8px;
}

.enc-row label {
  width: 90px;
  color: var(--text-dim);
  flex-shrink: 0;
  font-size: 12px;
  text-align: right;
}

.enc-row input[type="text"] {
  background: var(--surface-raised);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text);
  font-family: var(--font-mono);
  font-size: 13px;
  padding: 4px 8px;
  outline: none;
  flex: 1;
}

/* ── Status / error ───────────────────────────────────────────────────────── */

.status {
  color: var(--text-dim);
  font-size: 11px;
  margin-top: 8px;
  min-height: 16px;
  text-align: center;
}

.status.error {
  color: #ff6a6a;
}

/* ── Info tooltip ────────────────────────────────────────────────────────── */

.info-tip {
  position: relative;
  color: var(--text-dim);
  font-size: 12px;
  cursor: default;
  user-select: none;
  flex-shrink: 0;
  padding: 4px 6px;
}

.info-tip-text {
  display: none;
  position: absolute;
  top: calc(100% + 6px);
  left: 50%;
  transform: translateX(-50%);
  width: 220px;
  background: var(--surface-raised);
  border: 1px solid var(--border-light);
  border-radius: 4px;
  color: var(--text);
  font-size: 11px;
  line-height: 1.5;
  padding: 6px 8px;
  pointer-events: none;
  z-index: 10;
  white-space: normal;
}

.info-tip:hover .info-tip-text {
  display: block;
}

/* ── Misc ────────────────────────────────────────────────────────────────── */

.full-width {
  grid-column: 1 / -1;
}

.mb-12 {
  margin-bottom: 12px;
}