:root {
  --bg-primary: #18181b;
  --bg-secondary: #27272a;
  --bg-tertiary: #3f3f46;
  --bg-elevated: #202024;
  --text-main: #f4f4f5;
  --text-muted: #a1a1aa;
  --text-dim: #71717a;
  --accent-primary: #0284c7;
  --accent-hover: #0369a1;
  --accent-success: #16a34a;
  --accent-danger: #dc2626;
  --accent-warning: #d97706;
  --accent-js: #f7df1e;
  --accent-html: #e34f26;
  --accent-css: #1572b6;
  --border-color: #3f3f46;
  --border-subtle: #2d2d30;
  --console-bg: #111113;
  --console-border: #2a2a2e;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
  background-color: var(--bg-primary);
  color: var(--text-main);
  height: 100vh;
  display: flex;
  flex-direction: column;
  overflow: hidden;
  user-select: none;
}

/* Custom Scrollbars */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}
::-webkit-scrollbar-track {
  background: var(--bg-secondary);
}
::-webkit-scrollbar-thumb {
  background: var(--bg-tertiary);
  border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
  background: #52525b;
}

/* Header & Toolbar */
header {
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  padding: 6px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  flex-shrink: 0;
  z-index: 50;
  height: 48px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 14px;
}

.logo-area {
  display: flex;
  align-items: center;
  gap: 8px;
  cursor: default;
}

.logo-icon {
  background: #f7df1e;
  color: #000;
  font-weight: 900;
  font-size: 13px;
  border-radius: 4px;
  width: 26px;
  height: 26px;
  display: flex;
  align-items: center;
  justify-content: center;
  letter-spacing: -0.5px;
  box-shadow: 0 1px 3px rgba(0,0,0,0.3);
}

.logo-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-main);
  letter-spacing: -0.3px;
}

.logo-tag {
  background: rgba(2, 132, 199, 0.2);
  color: #38bdf8;
  border: 1px solid rgba(2, 132, 199, 0.4);
  font-size: 10.5px;
  font-weight: 600;
  padding: 2px 7px;
  border-radius: 12px;
}

/* Lesson Selector */
.lesson-control {
  display: flex;
  align-items: center;
  gap: 6px;
}

.dropdown {
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 5px 8px;
  border-radius: 5px;
  font-size: 12px;
  cursor: pointer;
  outline: none;
  transition: border-color 0.15s, box-shadow 0.15s;
  max-width: 250px;
}
.dropdown:hover, .dropdown:focus {
  border-color: var(--accent-primary);
}

/* Toolbar Buttons */
.toolbar {
  display: flex;
  align-items: center;
  gap: 6px;
}

.btn {
  background-color: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  color: var(--text-main);
  padding: 5px 10px;
  border-radius: 5px;
  font-size: 12px;
  font-weight: 600;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: all 0.15s ease;
  white-space: nowrap;
}
.btn:hover {
  background-color: #52525b;
  border-color: #71717a;
}
.btn:active {
  transform: translateY(1px);
}

.btn-primary {
  background-color: var(--accent-primary);
  border-color: #0369a1;
  color: #fff;
}
.btn-primary:hover {
  background-color: var(--accent-hover);
  border-color: #0284c7;
}

.btn-success {
  background-color: var(--accent-success);
  border-color: #15803d;
  color: #fff;
}
.btn-success:hover {
  background-color: #15803d;
}

.btn-danger {
  background-color: var(--accent-danger);
  border-color: #b91c1c;
  color: #fff;
}
.btn-danger:hover {
  background-color: #b91c1c;
}

.btn-outline {
  background: transparent;
  border-color: var(--border-color);
}
.btn-outline:hover {
  background-color: var(--bg-tertiary);
}

.autorun-toggle {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 11.5px;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px 8px;
  border-radius: 5px;
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--border-color);
}
.autorun-toggle input[type="checkbox"] {
  cursor: pointer;
  accent-color: var(--accent-primary);
}

/* Main Container Layout */
.main-container {
  display: flex;
  flex: 1;
  min-height: 0;
  height: calc(100vh - 48px - 26px);
  overflow: hidden;
  position: relative;
}

/* Left Pane (Code Editors & Task) */
.left-pane {
  width: 50%;
  min-width: 320px;
  max-width: calc(100% - 320px);
  display: flex;
  flex-direction: column;
  background-color: var(--bg-primary);
  border-right: 1px solid var(--border-color);
  position: relative;
}

/* Tab Bar */
.tab-bar {
  display: flex;
  align-items: center;
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  padding: 0 4px;
  height: 38px;
  flex-shrink: 0;
}

.tab-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 8px 14px;
  font-size: 12.5px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 7px;
  border-bottom: 2px solid transparent;
  height: 38px;
  transition: all 0.15s ease;
}
.tab-btn:hover {
  color: var(--text-main);
  background-color: rgba(255, 255, 255, 0.04);
}
.tab-btn.active {
  color: #fff;
  border-bottom-color: var(--accent-primary);
  background-color: var(--bg-primary);
}

.tab-btn.tab-html.active {
  border-bottom-color: var(--accent-html);
}
.tab-btn.tab-css.active {
  border-bottom-color: var(--accent-css);
}
.tab-btn.tab-js.active {
  border-bottom-color: var(--accent-js);
}
.tab-btn.tab-task.active {
  border-bottom-color: #a855f7;
}

.tab-tag {
  font-size: 10px;
  padding: 1px 5px;
  border-radius: 3px;
  font-weight: 700;
}
.tag-html { background: rgba(227, 79, 38, 0.2); color: #ff7a59; }
.tag-css { background: rgba(21, 114, 182, 0.25); color: #60a5fa; }
.tag-js { background: rgba(247, 223, 30, 0.2); color: #fde047; }
.tag-task { background: rgba(168, 85, 247, 0.2); color: #c084fc; }

.tab-actions {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 4px;
  padding-right: 6px;
}

.btn-icon {
  background: transparent;
  border: 1px solid transparent;
  color: var(--text-muted);
  padding: 4px 8px;
  border-radius: 4px;
  font-size: 11.5px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 5px;
  transition: all 0.15s ease;
}
.btn-icon:hover {
  color: var(--text-main);
  background: var(--bg-tertiary);
  border-color: var(--border-color);
}

/* Editor Wrapper */
.editor-container {
  flex: 1;
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.editor-pane {
  flex: 1;
  height: 100%;
  width: 100%;
  position: absolute;
  top: 0;
  left: 0;
  display: none;
}
.editor-pane.active {
  display: block;
}

/* CodeMirror customization */
.CodeMirror {
  height: 100% !important;
  font-family: "JetBrains Mono", "Fira Code", Consolas, "Courier New", monospace !important;
  font-size: 13.5px !important;
  line-height: 1.55 !important;
  background-color: #1e1e24 !important;
}
.CodeMirror-gutters {
  background-color: #191920 !important;
  border-right: 1px solid #2e2e38 !important;
}
.CodeMirror-linenumber {
  color: #636378 !important;
  padding: 0 8px 0 4px !important;
}
.CodeMirror-cursor {
  border-left: 2px solid #38bdf8 !important;
}

/* Task Tab Pane */
.task-pane {
  flex: 1;
  padding: 24px;
  overflow-y: auto;
  user-select: text;
  background-color: var(--bg-primary);
  line-height: 1.65;
  font-size: 14px;
  display: none;
}
.task-pane.active {
  display: block;
}
.task-pane h2 {
  font-size: 18px;
  margin-bottom: 12px;
  color: #fff;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.task-pane h3 {
  font-size: 15px;
  margin-top: 16px;
  margin-bottom: 8px;
  color: #38bdf8;
}
.task-pane p {
  margin-bottom: 12px;
  color: #d4d4d8;
}
.task-pane ul, .task-pane ol {
  margin-left: 20px;
  margin-bottom: 14px;
  color: #d4d4d8;
}
.task-pane li {
  margin-bottom: 4px;
}
.task-pane code {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  padding: 2px 6px;
  border-radius: 4px;
  font-family: monospace;
  font-size: 12.5px;
  color: #f7df1e;
}
.task-pane pre {
  background: #141416;
  border: 1px solid var(--border-color);
  padding: 12px;
  border-radius: 6px;
  margin: 12px 0;
  overflow-x: auto;
}
.task-pane pre code {
  background: transparent;
  border: none;
  padding: 0;
  color: #e4e4e7;
}

/* Student Tasks Card in Task Pane */
.tasks-card {
  background: #151922;
  border: 1px solid #0284c7;
  border-radius: 10px;
  padding: 16px;
  margin: 18px 0;
  box-shadow: 0 4px 16px rgba(2, 132, 199, 0.15);
}

.tasks-card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 12px;
  border-bottom: 1px solid rgba(2, 132, 199, 0.3);
  padding-bottom: 8px;
}

.tasks-card-title {
  font-size: 14.5px;
  font-weight: 700;
  color: #38bdf8;
  display: flex;
  align-items: center;
  gap: 8px;
}

.tasks-card-counter {
  font-size: 11.5px;
  color: #94a3b8;
  background: rgba(255, 255, 255, 0.05);
  padding: 2px 8px;
  border-radius: 12px;
  font-weight: 600;
}

.task-item {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid #27272a;
  border-radius: 8px;
  padding: 12px;
  margin-bottom: 10px;
  transition: all 0.2s ease;
}

.task-item:hover {
  border-color: #3f3f46;
  background: rgba(255, 255, 255, 0.05);
}

.task-item.completed {
  border-color: #16a34a;
  background: rgba(22, 163, 74, 0.08);
}

.task-item.completed .task-label {
  text-decoration: line-through;
  color: #a1a1aa;
}

.task-header {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  cursor: pointer;
}

.task-checkbox {
  margin-top: 3px;
  width: 16px;
  height: 16px;
  cursor: pointer;
  accent-color: #22c55e;
}

.task-label {
  font-weight: 600;
  font-size: 13.5px;
  color: #f4f4f5;
  flex: 1;
  transition: color 0.15s;
}

.task-desc {
  font-size: 13px;
  color: #cbd5e1;
  margin-top: 6px;
  margin-left: 26px;
  line-height: 1.5;
}

.task-hint {
  margin-top: 8px;
  margin-left: 26px;
  font-size: 12px;
}

.task-hint details {
  background: rgba(0, 0, 0, 0.25);
  border: 1px dashed #3f3f46;
  border-radius: 6px;
  padding: 6px 10px;
}

.task-hint summary {
  color: #fde047;
  cursor: pointer;
  font-weight: 600;
  outline: none;
}

.task-hint p {
  margin: 6px 0 0 0;
  color: #e4e4e7;
}

.theory-badge {
  display: inline-block;
  background: rgba(247, 223, 30, 0.15);
  color: #fde047;
  border: 1px solid rgba(247, 223, 30, 0.3);
  font-size: 11px;
  font-weight: 700;
  padding: 2px 8px;
  border-radius: 4px;
  margin-bottom: 10px;
}

/* Vertical Split Resizer */
.pane-resizer {
  width: 6px;
  background-color: var(--bg-secondary);
  cursor: col-resize;
  position: relative;
  flex-shrink: 0;
  transition: background-color 0.15s ease;
  z-index: 10;
  display: flex;
  align-items: center;
  justify-content: center;
}
.pane-resizer:hover, .pane-resizer.resizing {
  background-color: var(--accent-primary);
}
.pane-resizer-handle {
  width: 2px;
  height: 24px;
  background-color: var(--border-color);
  border-radius: 2px;
}

/* Right Pane (Preview & Console) */
.right-pane {
  flex: 1;
  min-width: 320px;
  display: flex;
  flex-direction: column;
  background-color: #2b2b32;
  overflow: hidden;
  position: relative;
}

/* Preview Header */
.preview-header {
  background-color: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
  padding: 4px 10px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 38px;
  flex-shrink: 0;
}

.preview-title {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 12.5px;
  font-weight: 600;
  color: var(--text-main);
}

.device-switcher {
  display: flex;
  align-items: center;
  gap: 2px;
  background-color: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: 5px;
  padding: 2px;
}

.device-btn {
  background: transparent;
  border: none;
  color: var(--text-muted);
  padding: 3px 7px;
  border-radius: 3px;
  font-size: 11px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 4px;
  transition: all 0.15s ease;
}
.device-btn:hover {
  color: var(--text-main);
}
.device-btn.active {
  background-color: var(--bg-tertiary);
  color: #fff;
  font-weight: 600;
}

/* Preview Viewport & Frame */
.preview-viewport {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: #1f1f24;
  overflow: hidden;
  position: relative;
  transition: padding 0.2s ease;
}

.preview-frame-wrapper {
  width: 100%;
  height: 100%;
  transition: width 0.2s cubic-bezier(0.4, 0, 0.2, 1), height 0.2s ease, box-shadow 0.2s ease;
  background: #ffffff;
  position: relative;
  display: flex;
}

.preview-frame-wrapper.device-desktop {
  width: 100%;
  height: 100%;
}
.preview-frame-wrapper.device-tablet {
  width: 768px;
  height: 96%;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
  border-radius: 8px;
  overflow: hidden;
  border: 4px solid #333;
}
.preview-frame-wrapper.device-mobile {
  width: 375px;
  height: 96%;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
  border-radius: 12px;
  overflow: hidden;
  border: 6px solid #333;
}

#preview-iframe {
  width: 100%;
  height: 100%;
  border: none;
  background-color: #ffffff;
}

/* Horizontal Sub-Resizer */
.console-resizer {
  height: 6px;
  background-color: var(--bg-secondary);
  cursor: row-resize;
  position: relative;
  flex-shrink: 0;
  transition: background-color 0.15s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}
.console-resizer:hover, .console-resizer.resizing {
  background-color: var(--accent-primary);
}
.console-resizer-handle {
  width: 24px;
  height: 2px;
  background-color: var(--border-color);
  border-radius: 2px;
}

/* Virtual Console Panel */
.console-pane {
  height: 180px;
  min-height: 80px;
  max-height: calc(100% - 100px);
  display: flex;
  flex-direction: column;
  background-color: var(--console-bg);
  border-top: 1px solid var(--console-border);
  flex-shrink: 0;
}

.console-header {
  background-color: #17171a;
  border-bottom: 1px solid var(--console-border);
  padding: 4px 10px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 32px;
  flex-shrink: 0;
}

.console-title {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 11.5px;
  font-weight: 600;
  color: var(--text-muted);
}

.badge-counter {
  background: rgba(220, 38, 38, 0.2);
  color: #f87171;
  font-size: 10px;
  padding: 1px 5px;
  border-radius: 10px;
  font-weight: 700;
  display: none;
}
.badge-counter.visible {
  display: inline-block;
}

.console-actions {
  display: flex;
  align-items: center;
  gap: 6px;
}

/* Console Logs List */
.console-logs {
  flex: 1;
  overflow-y: auto;
  padding: 6px 10px;
  font-family: "JetBrains Mono", Consolas, monospace;
  font-size: 12px;
  line-height: 1.5;
  user-select: text;
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.log-entry {
  display: flex;
  align-items: flex-start;
  gap: 8px;
  padding: 3px 6px;
  border-radius: 3px;
  border-left: 3px solid transparent;
  word-break: break-word;
}
.log-entry:hover {
  background: rgba(255, 255, 255, 0.03);
}

.log-time {
  color: var(--text-dim);
  font-size: 10px;
  flex-shrink: 0;
  margin-top: 2px;
}

.log-entry.log-info {
  border-left-color: #38bdf8;
  color: #e0f2fe;
}
.log-entry.log-log {
  border-left-color: #71717a;
  color: #e4e4e7;
}
.log-entry.log-warn {
  border-left-color: #f59e0b;
  background: rgba(245, 158, 11, 0.06);
  color: #fef08a;
}
.log-entry.log-error {
  border-left-color: #ef4444;
  background: rgba(239, 68, 68, 0.08);
  color: #fca5a5;
}
.log-entry.log-return {
  border-left-color: #10b981;
  color: #6ee7b7;
}

.log-content {
  flex: 1;
}

/* Console Input Bar */
.console-input-bar {
  display: flex;
  align-items: center;
  background-color: #17171a;
  border-top: 1px solid var(--console-border);
  padding: 4px 8px;
  gap: 6px;
  flex-shrink: 0;
}

.console-prompt {
  color: var(--accent-primary);
  font-family: monospace;
  font-size: 13px;
  font-weight: bold;
}

.console-input {
  flex: 1;
  background: transparent;
  border: none;
  color: #fff;
  font-family: "JetBrains Mono", Consolas, monospace;
  font-size: 12px;
  outline: none;
}
.console-input::placeholder {
  color: var(--text-dim);
}

/* Toast notifications */
.toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  background: #27272a;
  border: 1px solid #3f3f46;
  color: #fff;
  padding: 10px 16px;
  border-radius: 6px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.4);
  font-size: 12.5px;
  z-index: 1000;
  display: flex;
  align-items: center;
  gap: 8px;
  transform: translateY(100px);
  opacity: 0;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  pointer-events: none;
}
.toast.show {
  transform: translateY(0);
  opacity: 1;
}

/* Application Bottom Footer */
.app-footer {
  background-color: #18181b;
  border-top: 1px solid var(--border-color);
  padding: 4px 14px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  font-size: 11px;
  color: var(--text-muted);
  flex-shrink: 0;
  z-index: 50;
  user-select: none;
  min-height: 26px;
  height: 26px;
}

.footer-left {
  display: flex;
  align-items: center;
  gap: 6px;
  font-weight: 500;
  color: #e4e4e7;
  white-space: nowrap;
}

.footer-link {
  color: #38bdf8;
  text-decoration: none;
  font-weight: 600;
  transition: color 0.15s ease, text-decoration 0.15s ease;
}

.footer-link:hover {
  color: #7dd3fc;
  text-decoration: underline;
}

.footer-center {
  color: var(--text-muted);
  font-size: 11px;
  letter-spacing: 0.2px;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.footer-right {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 10.5px;
  color: #94a3b8;
  white-space: nowrap;
}

.footer-stat {
  color: #38bdf8;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  font-size: 10.5px;
  background: rgba(56, 189, 248, 0.1);
  padding: 1px 6px;
  border-radius: 3px;
  border: 1px solid rgba(56, 189, 248, 0.2);
}

.footer-sep {
  color: var(--border-color);
}

.footer-tip {
  color: #94a3b8;
}

.footer-right kbd {
  background: #27272a;
  border: 1px solid #52525b;
  border-radius: 3px;
  padding: 1px 4px;
  font-size: 9.5px;
  color: #f4f4f5;
  font-family: monospace;
}

@media (max-width: 960px) {
  .footer-center {
    display: none;
  }
}

@media (max-width: 680px) {
  .footer-tip,
  .footer-sep {
    display: none;
  }
}