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

:root {
  --bg: #0d1117;
  --surface: #161b22;
  --surface2: #21262d;
  --border: #30363d;
  --accent: #58a6ff;
  --green: #3fb950;
  --red: #f85149;
  --orange: #e3b341;
  --purple: #8957e5;
  --text: #c9d1d9;
  --dim: #8b949e;
  --r: 6px;
}

body {
  font-family: 'Segoe UI', system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden
}

/* ── Header ── */
header {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 0 20px;
  display: flex;
  align-items: center;
  gap: 16px;
  height: 52px;
  flex-shrink: 0
}

header h1 {
  font-size: 17px;
  font-weight: 700;
  color: var(--accent);
  letter-spacing: .4px;
  white-space: nowrap
}

nav {
  display: flex;
  gap: 4px
}

nav button {
  padding: 5px 14px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--dim);
  border-radius: var(--r);
  cursor: pointer;
  font-size: 13px;
  font-weight: 500;
  transition: all .15s
}

nav button:hover:not(.locked) {
  border-color: var(--accent);
  color: var(--text)
}

nav button.active {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff
}

nav button.locked {
  opacity: .38;
  cursor: default;
  position: relative
}

nav button.locked::after {
  content: 'soon';
  font-size: 8px;
  position: absolute;
  top: -5px;
  right: -2px;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 1px 3px;
  color: var(--dim)
}

/* ── Layout ── */
main {
  display: flex;
  flex: 1;
  overflow: hidden
}

#sidebar {
  width: 272px;
  background: var(--surface);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  flex-shrink: 0
}

#dfa-view {
  flex: 1;
  display: flex;
  flex-direction: column;
  overflow: hidden
}

#coming-soon {
  display: none;
  flex: 1;
  align-items: center;
  justify-content: center;
  flex-direction: column;
  gap: 14px
}

#coming-soon h2 {
  font-size: 26px;
  color: var(--dim)
}

#coming-soon p {
  color: var(--dim);
  font-size: 13px
}

/* ── Sidebar panels ── */
.panel {
  padding: 14px;
  border-bottom: 1px solid var(--border)
}

.panel h3 {
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--dim);
  margin-bottom: 10px
}

.row {
  display: flex;
  gap: 6px
}

.btn {
  width: 100%;
  padding: 7px 11px;
  border: 1px solid var(--border);
  background: var(--surface2);
  color: var(--text);
  border-radius: var(--r);
  cursor: pointer;
  font-size: 13px;
  text-align: left;
  display: flex;
  align-items: center;
  gap: 7px;
  transition: all .15s;
  margin-bottom: 5px
}

.btn:last-child {
  margin-bottom: 0
}

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

.btn.active {
  border-color: var(--accent);
  color: var(--accent);
  background: rgba(88, 166, 255, .1)
}

.btn.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  justify-content: center
}

.btn.primary:hover {
  background: #79b8ff;
  border-color: #79b8ff;
  color: #fff
}

.btn.danger:hover {
  border-color: var(--red);
  color: var(--red)
}

.btn.btn-half {
  width: 50%;
}

.label {
  font-size: 12px;
  color: var(--dim);
  margin-bottom: 4px
}

.igroup {
  display: flex;
  flex-direction: column;
  gap: 5px;
  margin-bottom: 9px
}

input[type=text],
select {
  width: 100%;
  padding: 6px 9px;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: var(--r);
  font-size: 13px
}

input:focus,
select:focus {
  outline: none;
  border-color: var(--accent)
}

select option {
  background: var(--surface2)
}

.hint {
  font-size: 11px;
  color: var(--dim);
  padding: 6px 8px;
  background: rgba(88, 166, 255, .04);
  border: 1px solid rgba(88, 166, 255, .12);
  border-radius: 4px;
  line-height: 1.5
}

/* ── State list ── */
.state-list {
  max-height: 150px;
  overflow-y: auto;
  margin-bottom: 8px
}

.sitem {
  display: flex;
  align-items: center;
  gap: 7px;
  padding: 4px 5px;
  border-radius: 4px;
  cursor: pointer;
  font-size: 12px;
  transition: background .1s
}

.sitem:hover {
  background: var(--surface2)
}

.sitem.sel {
  background: rgba(248, 81, 73, .1)
}

.sdot {
  width: 14px;
  height: 14px;
  border-radius: 50%;
  border: 1.5px solid;
  flex-shrink: 0
}

.sdot.normal {
  border-color: var(--border)
}

.sdot.start {
  border-color: var(--accent);
  background: rgba(88, 166, 255, .2)
}

.sdot.accept {
  border-color: var(--green);
  background: rgba(63, 185, 80, .2)
}

.sdot.both {
  border-color: var(--green);
  background: rgba(63, 185, 80, .2);
  box-shadow: 0 0 0 2px rgba(88, 166, 255, .4)
}

.stags {
  margin-left: auto;
  font-size: 10px;
  color: var(--dim)
}

/* ── Transition list ── */
.titem {
  display: flex;
  align-items: center;
  gap: 4px;
  padding: 3px 0;
  font-size: 12px
}

.titem .lbl {
  font-family: monospace;
  color: var(--accent)
}

.titem .sym {
  color: var(--dim)
}

.titem .del {
  margin-left: auto;
  background: none;
  border: none;
  color: var(--dim);
  cursor: pointer;
  font-size: 12px;
  padding: 0 2px;
  transition: color .1s
}

.titem .del:hover {
  color: var(--red)
}

/* ── Sim ── */
.sim-row {
  display: flex;
  align-items: center;
  gap: 6px;
  margin-top: 8px
}

.sim-row button {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--surface2);
  color: var(--text);
  cursor: pointer;
  font-size: 13px;
  flex-shrink: 0;
  transition: all .15s
}

.sim-row button:hover:not(:disabled) {
  border-color: var(--accent);
  color: var(--accent)
}

.sim-row button:disabled {
  opacity: .3;
  cursor: default
}

#step-ind {
  font-size: 12px;
  color: var(--dim);
  flex: 1;
  text-align: center
}

.result-box {
  margin-top: 8px;
  padding: 9px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--r);
  font-size: 12px;
  min-height: 48px
}

.badge {
  display: inline-block;
  padding: 2px 9px;
  border-radius: 20px;
  font-size: 11px;
  font-weight: 600
}

.badge.idle {
  background: var(--surface2);
  color: var(--dim);
  border: 1px solid var(--border)
}

.badge.ok {
  background: rgba(63, 185, 80, .18);
  color: var(--green);
  border: 1px solid rgba(63, 185, 80, .4)
}

.badge.fail {
  background: rgba(248, 81, 73, .18);
  color: var(--red);
  border: 1px solid rgba(248, 81, 73, .4)
}

.path-row {
  display: flex;
  flex-wrap: wrap;
  gap: 3px;
  margin-top: 6px
}

.pnode {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 3px;
  padding: 2px 7px;
  font-size: 11px;
  font-family: monospace;
  cursor: pointer;
  transition: all .15s
}

.pnode:hover {
  border-color: var(--accent)
}

.pnode.cur {
  border-color: var(--orange);
  color: var(--orange)
}

.pnode.fin {
  border-color: var(--green);
  color: var(--green)
}

.err-msg {
  color: var(--red);
  font-size: 11px;
  margin-top: 4px
}

/* ── Canvas ── */
.canvas-bar {
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  padding: 7px 16px;
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
  font-size: 12px;
  color: var(--dim)
}

#canvas-wrap {
  flex: 1;
  position: relative;
  overflow: hidden
}

canvas {
  display: block
}

canvas.sel-cur {
  cursor: default
}

canvas.grab-cur {
  cursor: grabbing
}

canvas.link-cur {
  cursor: cell
}

/* ── Symbol prompt overlay ── */
#sym-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, .55);
  z-index: 400;
  align-items: center;
  justify-content: center
}

#sym-overlay.show {
  display: flex
}

#sym-box {
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 20px 24px;
  min-width: 280px;
  box-shadow: 0 16px 48px rgba(0, 0, 0, .6)
}

#sym-box h4 {
  font-size: 13px;
  color: var(--text);
  margin-bottom: 12px
}

#sym-box .sym-from {
  font-family: monospace;
  color: var(--accent)
}

#sym-box .sym-arrow {
  color: var(--dim);
  margin: 0 6px
}

#sym-box .sym-to {
  font-family: monospace;
  color: var(--accent)
}

#sym-input {
  width: 100%;
  padding: 8px 10px;
  background: var(--bg);
  border: 1px solid var(--accent);
  color: var(--text);
  border-radius: var(--r);
  font-size: 14px;
  font-family: monospace;
  margin: 10px 0 14px;
  letter-spacing: .5px
}

#sym-input:focus {
  outline: none;
  border-color: #79b8ff
}

#sym-btns {
  display: flex;
  gap: 8px;
  justify-content: flex-end
}

#sym-btns button {
  padding: 6px 16px;
  border-radius: var(--r);
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  font-size: 13px;
  transition: all .15s
}

#sym-btns button.ok {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff
}

#sym-btns button.ok:hover {
  background: #79b8ff
}

#sym-btns button:not(.ok):hover {
  border-color: var(--dim);
  color: var(--text)
}

/* ── Context menu ── */
#ctx-menu {
  display: none;
  position: fixed;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 4px;
  min-width: 165px;
  z-index: 300;
  box-shadow: 0 8px 24px rgba(0, 0, 0, .5)
}

.cm-head {
  padding: 4px 10px;
  font-size: 11px;
  color: var(--dim);
  border-bottom: 1px solid var(--border);
  margin-bottom: 3px
}

.cm-item {
  padding: 7px 12px;
  cursor: pointer;
  font-size: 13px;
  border-radius: 4px;
  transition: background .1s
}

.cm-item:hover {
  background: var(--surface)
}

.cm-item.d {
  color: var(--red)
}

.cm-sep {
  border: none;
  border-top: 1px solid var(--border);
  margin: 3px 0
}

/* ── Scrollbar ── */
::-webkit-scrollbar {
  width: 5px
}

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

/* ── Classic (textbook) theme ── */
body.classic {
  --bg: #ffffff;
  --surface: #f4f4f4;
  --surface2: #e8e8e8;
  --border: #bbbbbb;
  --accent: #0055cc;
  --green: #006600;
  --red: #cc0000;
  --orange: #cc6600;
  --purple: #6600cc;
  --text: #111111;
  --dim: #555555;
}

body.classic header {
  border-bottom-color: #cccccc
}

body.classic #sidebar {
  border-right-color: #cccccc
}

body.classic .panel {
  border-bottom-color: #cccccc
}

body.classic ::-webkit-scrollbar-thumb {
  background: #cccccc
}

/* ── Theme toggle button ── */
#theme-btn {
  margin-left: auto;
  padding: 5px 13px;
  border: 1px solid var(--border);
  background: transparent;
  color: var(--dim);
  border-radius: var(--r);
  cursor: pointer;
  font-size: 12px;
  transition: all .15s;
  white-space: nowrap;
}

#theme-btn:hover {
  border-color: var(--accent);
  color: var(--text)
}

/* ── Reject state dot ── */
.sdot.reject {
  border-color: var(--red);
  background: rgba(248, 81, 73, .2)
}

/* ── PDA Stack ── */
.pda-cell {
  min-width: 28px;
  height: 28px;
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: monospace;
  font-size: 13px;
  border-radius: 3px;
  background: var(--surface2);
  flex-shrink: 0
}

.pda-cell.top {
  border-color: var(--accent);
  background: rgba(88, 166, 255, .2);
  color: var(--accent);
  font-weight: 700
}

/* ── TM Tape ── */
.tm-tape {
  display: flex;
  overflow-x: auto;
  gap: 2px;
  padding: 6px 0
}

.tm-cell {
  min-width: 28px;
  height: 28px;
  border: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: monospace;
  font-size: 13px;
  border-radius: 3px;
  background: var(--surface2);
  flex-shrink: 0
}

.tm-cell.head {
  border-color: var(--orange);
  background: rgba(227, 179, 65, .2);
  color: var(--orange);
  font-weight: 700
}

/* ════════════════════════════════════════════════════════════
   CFG Grammar View
   ════════════════════════════════════════════════════════════ */

#cfg-grammar-wrap {
  flex: 1;
  overflow-y: auto;
  padding: 20px 24px
}

/* ── Grammar table ── */
.cfg-table {
  width: 100%;
  border-collapse: collapse;
  font-family: 'Consolas', 'SF Mono', 'Courier New', monospace;
  font-size: 14px;
  table-layout: fixed
}

.cfg-table th {
  text-align: left;
  padding: 8px 14px;
  background: var(--surface);
  border-bottom: 2px solid var(--border);
  font-family: 'Segoe UI', system-ui, sans-serif;
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--dim);
  position: sticky;
  top: 0;
  z-index: 2
}

.cfg-table td {
  padding: 7px 14px;
  border-bottom: 1px solid var(--border);
  vertical-align: middle;
  transition: background .18s
}

.cfg-table td.var-col {
  width: 90px;
  color: var(--accent);
  font-weight: 700;
  white-space: nowrap
}

.cfg-table td.var-new {
  color: var(--green)
}

.cfg-table td.prod-col {
  color: var(--text);
  word-break: break-word;
  line-height: 1.9
}

/* ── Row-level diff highlights ── */
.cfg-row.added td {
  background: rgba(63, 185, 80, .07)
}

.cfg-row.modified td {
  background: rgba(227, 179, 65, .08)
}

/* ── Per-production span highlights ── */
.cfg-prod {
  display: inline-block;
  padding: 2px 6px;
  border-radius: 3px;
  margin: 1px 2px;
  border: 1px solid transparent;
  transition: all .15s
}

.cfg-prod.added {
  background: rgba(63, 185, 80, .15);
  border-color: rgba(63, 185, 80, .35);
  color: var(--green)
}

.cfg-prod.modified {
  background: rgba(227, 179, 65, .15);
  border-color: rgba(227, 179, 65, .35);
  color: var(--orange)
}

.cfg-prod.removed {
  background: rgba(248, 81, 73, .10);
  border-color: rgba(248, 81, 73, .25);
  color: var(--red);
  text-decoration: line-through;
  opacity: .75
}

.cfg-prod-sep {
  color: var(--dim);
  font-size: 13px
}

/* ── Empty state ── */
.cfg-empty {
  text-align: center;
  padding: 70px 24px;
  color: var(--dim);
  font-size: 14px;
  line-height: 1.7
}

/* ── Sidebar textarea ── */
#cfg-textarea {
  width: 100%;
  background: var(--bg);
  border: 1px solid var(--border);
  color: var(--text);
  border-radius: var(--r);
  font-family: 'Consolas', 'SF Mono', 'Courier New', monospace;
  font-size: 13px;
  padding: 8px 10px;
  resize: vertical;
  line-height: 1.6;
  min-height: 110px
}

#cfg-textarea:focus {
  outline: none;
  border-color: var(--accent)
}

/* ── Classic theme overrides ── */
body.classic .cfg-row.added td {
  background: rgba(0, 102, 0, .07)
}

body.classic .cfg-row.modified td {
  background: rgba(204, 102, 0, .08)
}

body.classic .cfg-prod.added {
  background: rgba(0, 102, 0, .12);
  border-color: rgba(0, 102, 0, .30);
  color: var(--green)
}

body.classic .cfg-prod.modified {
  background: rgba(204, 102, 0, .12);
  border-color: rgba(204, 102, 0, .30);
  color: var(--orange)
}

body.classic .cfg-prod.removed {
  background: rgba(204, 0, 0, .09);
  border-color: rgba(204, 0, 0, .25);
  color: var(--red)
}