:root {
  --bg: #fff;
  --bg-secondary: #fafafa;
  --bg-error: #fff5f5;
  --text: #222;
  --text-secondary: #555;
  --text-muted: #888;
  --text-placeholder: #bbb;
  --border: #ddd;
  --border-light: #eee;
  --border-error: #ecc;
  --border-focus: #888;
  --btn-bg: #fff;
  --btn-border: #ccc;
  --btn-hover: #f5f5f5;
  --btn-primary-bg: #222;
  --btn-primary-text: #fff;
  --btn-primary-hover: #444;
  --btn-primary-border-hover: #444;
  --error-text: #c33;
  --footer-text: #aaa;
  --footer-link: #555;
  --input-focus-shadow: rgba(0,0,0,0.06);
  --highlight-bg: rgba(74, 158, 255, 0.2);
  --highlight-outline: rgba(74, 158, 255, 0.5);
  --mode-btn-active-bg: #222;
  --mode-btn-active-text: #fff;
  --mode-btn-active-border: #222;
  --mode-btn-active-hover-bg: #444;
  --stop-bg: #c33;
  --stop-text: #fff;
  --stop-hover-bg: #d44;
  --pause-bg: #e6a817;
  --pause-text: #fff;
  --pause-hover-bg: #f0b828;
  --viewer-bg: transparent;
}

[data-theme="dark"] {
  --bg: #1a1a2e;
  --bg-secondary: #16213e;
  --bg-error: #2d1f1f;
  --text: #e0e0e0;
  --text-secondary: #aaa;
  --text-muted: #6a6a7a;
  --text-placeholder: #555;
  --border: #2e2e42;
  --border-light: #252540;
  --border-error: #5c3333;
  --border-focus: #5a5a7a;
  --btn-bg: #252540;
  --btn-border: #3a3a5a;
  --btn-hover: #30304a;
  --btn-primary-bg: #4a9eff;
  --btn-primary-text: #fff;
  --btn-primary-hover: #6db5ff;
  --btn-primary-border-hover: #6db5ff;
  --error-text: #ff6b6b;
  --footer-text: #4a4a5a;
  --footer-link: #7a7a9a;
  --input-focus-shadow: rgba(74,158,255,0.1);
  --highlight-bg: rgba(74, 158, 255, 0.3);
  --highlight-outline: rgba(74, 158, 255, 0.6);
  --mode-btn-active-bg: #4a9eff;
  --mode-btn-active-text: #fff;
  --mode-btn-active-border: #4a9eff;
  --mode-btn-active-hover-bg: #6db5ff;
  --stop-bg: #c33;
  --stop-text: #fff;
  --stop-hover-bg: #d44;
  --pause-bg: #b88a0e;
  --pause-text: #fff;
  --pause-hover-bg: #c99a1a;
  --viewer-bg: transparent;
}

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

body {
  font-family: -apple-system, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  transition: background 0.2s, color 0.2s;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 32px 20px 40px;
}

header {
  margin-bottom: 28px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border);
}

header h1 {
  font-size: 22px;
  font-weight: 500;
  color: var(--text);
}

.toolbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 14px;
}

.toolbar-left {
  display: flex;
  gap: 16px;
  align-items: center;
}

.toolbar-right {
  display: flex;
  gap: 8px;
}

button {
  padding: 6px 16px;
  border: 1px solid var(--btn-border);
  border-radius: 4px;
  font-size: 13px;
  cursor: pointer;
  background: var(--btn-bg);
  color: var(--text);
  transition: background 0.15s, border-color 0.15s;
}

button:hover {
  background: var(--btn-hover);
}

.btn-primary {
  background: var(--btn-primary-bg);
  color: var(--btn-primary-text);
  border-color: var(--btn-primary-bg);
}

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

.btn-stop {
  background: var(--stop-bg);
  color: var(--stop-text);
  border-color: var(--stop-bg);
}

.btn-stop:hover {
  background: var(--stop-hover-bg);
  border-color: var(--stop-hover-bg);
}

.btn-pause {
  background: var(--pause-bg);
  color: var(--pause-text);
  border-color: var(--pause-bg);
}

.btn-pause:hover {
  background: var(--pause-hover-bg);
  border-color: var(--pause-hover-bg);
}

#theme-toggle {
  padding: 6px 10px;
  font-size: 14px;
  line-height: 1;
}

/* ── Run mode toggle ─────────────────────────────────────── */

.run-mode-toggle {
  display: flex;
  gap: 0;
  border: 1px solid var(--btn-border);
  border-radius: 4px;
  overflow: hidden;
}

.mode-btn {
  padding: 5px 12px;
  font-size: 12px;
  border: none;
  border-radius: 0;
  background: var(--btn-bg);
  color: var(--text-secondary);
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}

.mode-btn.active {
  background: var(--mode-btn-active-bg);
  color: var(--mode-btn-active-text);
  border-color: var(--mode-btn-active-border);
}

.mode-btn.active:hover {
  background: var(--mode-btn-active-hover-bg);
}

/* ── Visual panel ────────────────────────────────────────── */

.visual-panel {
  margin-bottom: 14px;
}

.visual-controls {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 6px;
}

.visual-controls label {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--text-secondary);
}

.visual-controls input[type="range"] {
  width: 100px;
  accent-color: var(--btn-primary-bg);
}

#speed-label {
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: 12px;
  color: var(--text-muted);
  min-width: 38px;
}

/* ── Code viewer ─────────────────────────────────────────── */

.code-viewer {
  padding: 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 4px;
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: 13px;
  line-height: 2;
  min-height: 40px;
  max-height: 300px;
  overflow-y: auto;
  display: flex;
  flex-wrap: wrap;
  align-items: flex-start;
  gap: 4px;
  transition: background 0.2s, border-color 0.15s;
}

.instr {
  display: inline-block;
  padding: 1px 3px;
  border-radius: 3px;
  background: var(--viewer-bg);
  transition: background 0.08s, outline-color 0.08s;
  white-space: pre;
}

.instr.active {
  background: var(--highlight-bg);
  outline: 1px solid var(--highlight-outline);
  outline-offset: -1px;
}

/* ── Panels ──────────────────────────────────────────────── */

.panel-header {
  font-size: 12px;
  color: var(--text-muted);
  margin-bottom: 4px;
}

.editor-panel,
.input-panel,
.output-panel {
  margin-bottom: 14px;
}

#source-editor {
  width: 100%;
  min-height: 200px;
  padding: 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text);
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: 13px;
  line-height: 1.5;
  resize: vertical;
  transition: border-color 0.15s, background 0.2s, color 0.2s;
}

#source-editor:focus {
  outline: none;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--input-focus-shadow);
}

#source-editor::placeholder {
  color: var(--text-placeholder);
}

#input-editor {
  width: 100%;
  padding: 10px 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 4px;
  color: var(--text);
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: 13px;
  resize: vertical;
  transition: border-color 0.15s, background 0.2s, color 0.2s;
}

#input-editor:focus {
  outline: none;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px var(--input-focus-shadow);
}

#input-editor::placeholder {
  color: var(--text-placeholder);
}

.output-area {
  min-height: 40px;
  padding: 12px;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 4px;
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: 13px;
  white-space: pre-wrap;
  word-break: break-all;
  color: var(--text);
  transition: background 0.2s, color 0.2s, border-color 0.15s;
}

.output-area:empty::before {
  content: "No output";
  color: var(--text-placeholder);
}

/* ── Error area ──────────────────────────────────────────── */

.error-area {
  margin-top: 6px;
  padding: 10px 12px;
  background: var(--bg-error);
  border: 1px solid var(--border-error);
  border-radius: 4px;
  color: var(--error-text);
  font-family: "SF Mono", "Cascadia Code", "Consolas", monospace;
  font-size: 13px;
  white-space: pre-wrap;
  transition: background 0.2s, color 0.2s, border-color 0.15s;
}

/* ── Footer ──────────────────────────────────────────────── */

footer {
  text-align: center;
  margin-top: 28px;
  padding-top: 12px;
  border-top: 1px solid var(--border-light);
  font-size: 11px;
  color: var(--footer-text);
}

footer a {
  color: var(--footer-link);
  text-decoration: none;
}

footer a:hover {
  text-decoration: underline;
}