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

:root {
  --bg: #0f1117;
  --surface: #1a1d27;
  --border: #2a2d3a;
  --text: #e1e4ed;
  --text-dim: #8b8fa3;
  --accent: #6c8cff;
  --accent-hover: #8ba3ff;
  --green: #4ade80;
  --red: #f87171;
  --yellow: #fbbf24;
  --highlight: #2a3a5c;
}

body {
  font-family: 'SF Mono', 'Fira Code', 'Cascadia Code', monospace;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  padding: 1.5rem;
  max-width: 960px;
  margin: 0 auto;
}

header {
  margin-bottom: 1.5rem;
}

header h1 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent);
}

header p {
  color: var(--text-dim);
  font-size: 0.85rem;
  margin-top: 0.25rem;
}

h2 {
  font-size: 0.9rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-dim);
  margin-bottom: 0.5rem;
}

/* Editor */
.editor-panel {
  margin-bottom: 1rem;
}

.panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

textarea {
  width: 100%;
  height: 200px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  color: var(--text);
  font-family: inherit;
  font-size: 0.9rem;
  padding: 1rem;
  resize: vertical;
  outline: none;
  line-height: 1.6;
}

textarea:focus {
  border-color: var(--accent);
}

textarea::placeholder {
  color: var(--text-dim);
  opacity: 0.5;
}

.error {
  color: var(--red);
  font-size: 0.8rem;
  margin-top: 0.5rem;
  min-height: 1.2em;
}

/* Controls */
.control-panel {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.controls {
  display: flex;
  gap: 0.5rem;
}

button {
  font-family: inherit;
  font-size: 0.8rem;
  padding: 0.5rem 1rem;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s;
}

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

button:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

#btn-assemble {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  font-weight: 600;
}

#btn-assemble:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: #fff;
}

.speed-control {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8rem;
  color: var(--text-dim);
}

.speed-control input[type="range"] {
  width: 100px;
  accent-color: var(--accent);
}

/* State panel */
.state-panel {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1rem;
  margin-bottom: 1.5rem;
}

@media (max-width: 700px) {
  .state-panel {
    grid-template-columns: 1fr;
  }
}

/* Registers */
.reg-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.35rem;
}

.reg-cell {
  display: flex;
  justify-content: space-between;
  padding: 0.4rem 0.6rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.85rem;
}

.reg-cell .reg-name {
  color: var(--text-dim);
}

.reg-cell .reg-val {
  font-weight: 600;
  color: var(--text);
}

.reg-cell.changed {
  border-color: var(--accent);
  background: var(--highlight);
}

.reg-cell.changed .reg-val {
  color: var(--accent);
}

/* Program list */
.program-list {
  max-height: 260px;
  overflow-y: auto;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--surface);
}

.program-list .inst-row {
  display: flex;
  gap: 0.75rem;
  padding: 0.35rem 0.6rem;
  font-size: 0.8rem;
  border-bottom: 1px solid var(--border);
}

.program-list .inst-row:last-child {
  border-bottom: none;
}

.program-list .inst-row.active {
  background: var(--highlight);
  border-left: 3px solid var(--accent);
}

.inst-row .inst-addr {
  color: var(--text-dim);
  min-width: 1.5rem;
}

.inst-row .inst-hex {
  color: var(--yellow);
  min-width: 3rem;
}

.inst-row .inst-asm {
  color: var(--text);
}

.pc-badge {
  font-size: 0.75rem;
  background: var(--accent);
  color: #fff;
  padding: 0.15rem 0.5rem;
  border-radius: 4px;
  margin-left: 0.5rem;
  font-weight: 600;
}

/* Display output */
.display-output {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem;
  min-height: 60px;
  font-size: 1.5rem;
  font-weight: 700;
  letter-spacing: 0.3em;
  color: var(--green);
  word-break: break-all;
}

/* Machine code */
.machine-code-panel {
  margin-bottom: 1.5rem;
}

.machine-code {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.75rem;
  font-size: 0.8rem;
  color: var(--text-dim);
  line-height: 1.6;
  max-height: 150px;
  overflow-y: auto;
}

.machine-code .mc-row {
  display: flex;
  gap: 1rem;
}

.machine-code .mc-addr {
  color: var(--text-dim);
  min-width: 2rem;
}

.machine-code .mc-hex {
  color: var(--yellow);
  min-width: 3.5rem;
}

.machine-code .mc-bin {
  color: var(--text-dim);
}

/* Footer */
footer {
  text-align: center;
  padding: 1rem 0;
  border-top: 1px solid var(--border);
  margin-top: 1rem;
}

footer a {
  color: var(--text-dim);
  text-decoration: none;
  font-size: 0.8rem;
}

footer a:hover {
  color: var(--accent);
}