/* Modern Dark Theme Design System */
:root {
    --bg-app: hsl(222, 25%, 10%);
    --bg-panel: hsl(222, 22%, 13%);
    --bg-panel-hover: hsl(222, 20%, 16%);
    --bg-input: hsl(222, 20%, 8%);
    --border-color: hsl(222, 15%, 20%);
    --border-color-focus: hsl(210, 100%, 60%);
    
    --text-primary: hsl(210, 20%, 95%);
    --text-secondary: hsl(210, 10%, 70%);
    --text-muted: hsl(210, 10%, 45%);
    
    --color-brand: hsl(210, 100%, 60%); /* Indigo/Blue */
    --color-success: hsl(142, 70%, 45%); /* Emerald green */
    --color-warning: hsl(38, 92%, 50%); /* Amber */
    --color-danger: hsl(350, 80%, 55%); /* Crimson red */
    
    --badge-easy: hsl(142, 60%, 15%);
    --badge-easy-text: hsl(142, 70%, 55%);
    --badge-medium: hsl(38, 70%, 12%);
    --badge-medium-text: hsl(38, 90%, 55%);
    --badge-hard: hsl(350, 60%, 15%);
    --badge-hard-text: hsl(350, 80%, 55%);
    
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --font-title: 'Outfit', sans-serif;
    --font-mono: 'Fira Code', monospace;
    
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.2), 0 2px 4px -1px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.3), 0 4px 6px -2px rgba(0, 0, 0, 0.15);
    --border-radius: 8px;
    --transition-speed: 0.2s;
}

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

body {
    background-color: var(--bg-app);
    color: var(--text-primary);
    font-family: var(--font-sans);
    height: 100vh;
    overflow: hidden;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

/* Scrollbar Customization */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}
::-webkit-scrollbar-track {
    background: transparent;
}
::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 10px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}

/* App Container Layout */
.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

/* App Header styling */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
    padding: 0 24px;
    background-color: var(--bg-panel);
    border-bottom: 1px stroke var(--border-color);
    box-shadow: var(--shadow-sm);
    z-index: 10;
    flex-shrink: 0;
    border-bottom: 1px solid var(--border-color);
}

.brand {
    display: flex;
    align-items: center;
    gap: 12px;
}

.brand-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: 8px;
    background-color: hsla(210, 100%, 60%, 0.1);
    color: var(--color-brand);
}

.brand-text h1 {
    font-family: var(--font-title);
    font-size: 16px;
    font-weight: 700;
    letter-spacing: -0.2px;
    line-height: 1.2;
}

.brand-text span {
    font-size: 11px;
    color: var(--text-muted);
    font-weight: 500;
}

/* Status Panel */
.status-panel {
    display: flex;
    align-items: center;
    gap: 20px;
}

.status-badge {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 6px 12px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
}

.status-badge .pulse {
    width: 8px;
    height: 8px;
    border-radius: 50%;
}

.status-idle .pulse { background-color: var(--text-muted); }
.status-idle { color: var(--text-secondary); }

.status-running .pulse {
    background-color: var(--color-success);
    animation: pulse-animation 1.5s infinite;
}
.status-running {
    color: var(--color-success);
    border-color: hsla(142, 70%, 45%, 0.2);
}

.status-paused .pulse { background-color: var(--color-warning); }
.status-paused {
    color: var(--color-warning);
    border-color: hsla(38, 92%, 50%, 0.2);
}

@keyframes pulse-animation {
    0% { transform: scale(0.95); box-shadow: 0 0 0 0 rgba(74, 222, 128, 0.7); }
    70% { transform: scale(1); box-shadow: 0 0 0 6px rgba(74, 222, 128, 0); }
    100% { transform: scale(0.95); box-shadow: 0 0 0 0 rgba(74, 222, 128, 0); }
}

.progress-container {
    width: 240px;
}

.progress-header {
    display: flex;
    justify-content: space-between;
    font-size: 11px;
    color: var(--text-secondary);
    font-weight: 500;
    margin-bottom: 4px;
}

.progress-bar {
    height: 6px;
    background-color: var(--bg-input);
    border-radius: 3px;
    overflow: hidden;
}

#progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-brand), hsl(210, 100%, 70%));
    border-radius: 3px;
    transition: width 0.4s ease;
}

/* Workspace Layout */
.app-workspace {
    display: flex;
    flex-1: 1;
    overflow: hidden;
    height: calc(100vh - 64px);
}

.workspace-column {
    display: flex;
    flex-direction: column;
    height: 100%;
    overflow: hidden;
}

.controls-column {
    width: 320px;
    border-right: 1px solid var(--border-color);
    flex-shrink: 0;
}

.explorer-column {
    flex: 1.2;
    border-right: 1px solid var(--border-color);
    min-width: 380px;
}

.viewer-column {
    flex: 1.8;
    min-width: 450px;
}

/* Panel Styles */
.panel {
    background-color: var(--bg-panel);
    border-radius: 0;
    display: flex;
    flex-direction: column;
    overflow: hidden;
}

.control-panel {
    padding: 20px;
    border-bottom: 1px solid var(--border-color);
    gap: 16px;
}

.control-panel h2, .console-panel h2, .explorer-panel h2, .viewer-panel h2 {
    font-family: var(--font-title);
    font-size: 15px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-secondary);
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 20px;
    border-bottom: 1px solid var(--border-color);
    flex-shrink: 0;
}

/* Console logs panel */
.console-panel {
    flex: 1;
}

.console-box {
    flex: 1;
    background-color: var(--bg-input);
    font-family: var(--font-mono);
    font-size: 11px;
    padding: 16px;
    overflow-y: auto;
    color: var(--text-secondary);
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.log-entry {
    word-break: break-all;
    white-space: pre-wrap;
    line-height: 1.4;
}

.log-info { color: var(--text-secondary); }
.log-warning { color: var(--color-warning); }
.log-error { color: var(--color-danger); font-weight: bold; }
.log-success { color: var(--color-success); }

/* Buttons styling */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    border: none;
    border-radius: var(--border-radius);
    padding: 8px 16px;
    font-family: var(--font-sans);
    font-size: 13px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed);
    text-decoration: none;
    outline: none;
}

.btn-primary {
    background-color: var(--color-brand);
    color: white;
}
.btn-primary:hover:not(:disabled) {
    background-color: hsl(210, 100%, 65%);
}

.btn-warning {
    background-color: var(--color-warning);
    color: var(--bg-app);
}
.btn-warning:hover:not(:disabled) {
    background-color: hsl(38, 92%, 55%);
}

.btn-danger {
    background-color: var(--color-danger);
    color: white;
}
.btn-danger:hover:not(:disabled) {
    background-color: hsl(350, 80%, 60%);
}

.btn-secondary {
    background-color: var(--border-color);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}
.btn-secondary:hover:not(:disabled) {
    background-color: var(--bg-panel-hover);
}

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
}
.btn-outline:hover:not(:disabled) {
    border-color: var(--text-muted);
    color: var(--text-primary);
}

.btn-icon {
    background: transparent;
    border: none;
    cursor: pointer;
    color: var(--text-muted);
    border-radius: 4px;
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition-speed);
}
.btn-icon:hover {
    background-color: var(--border-color);
    color: var(--text-primary);
}

.btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.w-100 { width: 100%; }

.control-buttons {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 8px;
}

.selection-status {
    background-color: var(--bg-input);
    border-radius: var(--border-radius);
    padding: 10px 14px;
    font-size: 11px;
    color: var(--text-muted);
    display: flex;
    justify-content: space-between;
    align-items: center;
    border: 1px solid var(--border-color);
}

.actions-group {
    margin-top: 4px;
}

/* Explorer Column Styles */
.explorer-panel {
    height: 100%;
}

.explorer-header {
    flex-wrap: wrap;
    gap: 12px;
}

.search-bar {
    position: relative;
    width: 220px;
}

.search-bar input {
    width: 100%;
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 8px 12px 8px 36px;
    color: var(--text-primary);
    font-family: var(--font-sans);
    font-size: 12px;
    outline: none;
    transition: all var(--transition-speed);
}

.search-bar input:focus {
    border-color: var(--color-brand);
    box-shadow: 0 0 0 2px hsla(210, 100%, 60%, 0.15);
}

.search-icon {
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    pointer-events: none;
}

.explorer-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 20px;
    background-color: var(--bg-input);
    border-bottom: 1px solid var(--border-color);
    font-size: 11px;
    color: var(--text-muted);
    font-weight: 500;
}

/* Tree Component styling */
.tree-container {
    flex: 1;
    overflow-y: auto;
    padding: 12px 0;
}

.tree-node-category {
    margin-bottom: 4px;
}

.tree-node-header {
    display: flex;
    align-items: center;
    padding: 8px 20px 8px 16px;
    cursor: pointer;
    font-weight: 600;
    font-size: 13px;
    user-select: none;
    transition: background-color var(--transition-speed);
    gap: 8px;
}

.tree-node-header:hover {
    background-color: var(--bg-panel-hover);
}

.tree-node-arrow {
    display: flex;
    align-items: center;
    color: var(--text-muted);
    transition: transform var(--transition-speed);
}

.tree-node-category.expanded > .tree-node-header .tree-node-arrow {
    transform: rotate(90deg);
}

.tree-node-title {
    flex: 1;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.tree-node-count {
    font-size: 10px;
    color: var(--text-muted);
    background-color: var(--bg-input);
    padding: 2px 6px;
    border-radius: 10px;
    border: 1px solid var(--border-color);
}

/* Subcategories */
.tree-children-subcategories {
    display: none;
    padding-left: 16px;
    border-left: 1px dashed var(--border-color);
    margin-left: 22px;
}

.tree-node-category.expanded > .tree-children-subcategories {
    display: block;
}

.tree-node-subcategory {
    margin-top: 4px;
}

.tree-children-problems {
    display: none;
    padding-left: 16px;
    border-left: 1px dashed var(--border-color);
    margin-left: 22px;
}

.tree-node-subcategory.expanded > .tree-children-problems {
    display: block;
}

/* Problems list item */
.problem-item {
    display: flex;
    align-items: center;
    padding: 6px 16px 6px 12px;
    border-radius: 4px;
    font-size: 12.5px;
    color: var(--text-secondary);
    gap: 10px;
    cursor: pointer;
    margin-right: 12px;
}

.problem-item:hover {
    background-color: var(--bg-panel-hover);
    color: var(--text-primary);
}

.problem-item.active {
    background-color: hsla(210, 100%, 60%, 0.08);
    color: var(--text-primary);
    font-weight: 500;
}

.problem-status {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: var(--border-color);
    flex-shrink: 0;
}

.problem-item.scraped .problem-status {
    background-color: var(--color-success);
    box-shadow: 0 0 4px var(--color-success);
}

.problem-title {
    flex: 1;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* Difficulty badges */
.badge {
    font-size: 10px;
    font-weight: 600;
    padding: 2px 6px;
    border-radius: 4px;
    text-transform: uppercase;
}

.difficulty-easy {
    background-color: var(--badge-easy);
    color: var(--badge-easy-text);
}
.difficulty-medium {
    background-color: var(--badge-medium);
    color: var(--badge-medium-text);
}
.difficulty-hard {
    background-color: var(--badge-hard);
    color: var(--badge-hard-text);
}

/* Loading and empty states */
.loading-state, .empty-state-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px;
    text-align: center;
    color: var(--text-muted);
    height: 100%;
}

.spinner {
    width: 24px;
    height: 24px;
    border: 2.5px solid var(--border-color);
    border-top: 2.5px solid var(--color-brand);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
    margin-bottom: 12px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Checkbox Customization */
.checkbox-container {
    display: inline-flex;
    align-items: center;
    position: relative;
    padding-left: 22px;
    cursor: pointer;
    user-select: none;
}

.checkbox-container input {
    position: absolute;
    opacity: 0;
    cursor: pointer;
    height: 0;
    width: 0;
}

.checkmark {
    position: absolute;
    left: 0;
    height: 14px;
    width: 14px;
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: 3px;
}

.checkbox-container:hover input ~ .checkmark {
    border-color: var(--text-muted);
}

.checkbox-container input:checked ~ .checkmark {
    background-color: var(--color-brand);
    border-color: var(--color-brand);
}

.checkbox-container input:indeterminate ~ .checkmark {
    background-color: var(--color-brand);
    border-color: var(--color-brand);
}

.checkmark:after {
    content: "";
    position: absolute;
    display: none;
}

.checkbox-container input:checked ~ .checkmark:after {
    display: block;
}

.checkbox-container input:indeterminate ~ .checkmark:after {
    display: block;
    left: 4px;
    top: 5px;
    width: 6px;
    height: 2px;
    border: none;
    background-color: white;
    transform: none;
}

.checkbox-container .checkmark:after {
    left: 4px;
    top: 1px;
    width: 4px;
    height: 7px;
    border: solid white;
    border-width: 0 1.5px 1.5px 0;
    transform: rotate(45deg);
}

.problem-item .checkbox-container {
    padding-left: 14px;
}

.problem-item .checkmark {
    width: 14px;
    height: 14px;
}

/* Viewer Panel Column Styles */
.viewer-panel {
    height: 100%;
    padding: 24px;
    overflow-y: auto;
}

.empty-viewer {
    display: flex;
    align-items: center;
    justify-content: center;
    background-color: var(--bg-panel);
}

.empty-state-icon {
    color: var(--border-color-focus);
    opacity: 0.6;
    margin-bottom: 16px;
}

.empty-state-content h3 {
    font-family: var(--font-title);
    color: var(--text-primary);
    font-size: 18px;
    margin-bottom: 8px;
}

.empty-state-content p {
    font-size: 13px;
    max-width: 320px;
    margin: 0 auto;
}

/* Viewer Loaded Content */
.viewer-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 12px;
}

.viewer-meta-left {
    display: flex;
    align-items: center;
    gap: 8px;
}

.meta-path {
    font-size: 11px;
    color: var(--text-muted);
    font-weight: 500;
}

.viewer-links {
    display: flex;
    gap: 8px;
}

.link-external {
    font-size: 11.5px;
    padding: 4px 10px;
    border-radius: 4px;
    color: var(--text-secondary);
    background-color: var(--bg-input);
    border: 1px solid var(--border-color);
}
.link-external:hover {
    color: var(--text-primary);
    background-color: var(--border-color);
}

#viewer-content-state h2 {
    font-family: var(--font-title);
    font-size: 22px;
    font-weight: 700;
    letter-spacing: -0.4px;
    margin-bottom: 16px;
    color: var(--text-primary);
}

/* Approach Selector dropdown */
.approach-selector-container {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
    background-color: var(--bg-input);
    padding: 8px 16px;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
}

.approach-selector-container label {
    font-size: 12.5px;
    font-weight: 600;
    color: var(--text-secondary);
}

.form-select {
    background-color: var(--bg-panel);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    color: var(--text-primary);
    padding: 4px 12px;
    font-family: var(--font-sans);
    font-size: 12.5px;
    outline: none;
    cursor: pointer;
    min-width: 180px;
}
.form-select:focus {
    border-color: var(--color-brand);
}

/* Code area container */
.code-container-panel {
    display: flex;
    flex-direction: column;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    background-color: var(--bg-input);
    overflow: hidden;
    margin-bottom: 20px;
    box-shadow: var(--shadow-md);
}

.code-header-tabs {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: var(--bg-panel);
    padding: 0 16px;
    border-bottom: 1px solid var(--border-color);
    height: 40px;
}

.lang-tabs {
    display: flex;
    gap: 4px;
    height: 100%;
}

.tab-btn {
    background: transparent;
    border: none;
    border-bottom: 2px solid transparent;
    color: var(--text-muted);
    font-family: var(--font-sans);
    font-size: 12px;
    font-weight: 600;
    padding: 0 12px;
    cursor: pointer;
    transition: all var(--transition-speed);
}

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

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

.code-editor-area {
    padding: 16px;
    overflow-x: auto;
    max-height: 480px;
}

.code-editor-area pre {
    margin: 0;
}

.code-editor-area code {
    font-family: var(--font-mono);
    font-size: 12px;
    white-space: pre;
    color: hsl(210, 15%, 85%);
}

/* Complexity Panel formatting */
.complexity-section {
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background-color: var(--bg-input);
    padding: 16px 20px;
}

.complexity-section h3 {
    font-family: var(--font-title);
    font-size: 13.5px;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.complexity-box {
    font-size: 12.5px;
    color: var(--text-secondary);
    line-height: 1.6;
}

/* Solved status icon in tree */
.solved-status-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    border: 1px solid var(--border-color);
    color: transparent;
    cursor: pointer;
    transition: all var(--transition-speed);
    flex-shrink: 0;
    margin-left: auto;
}

.solved-status-icon:hover {
    border-color: var(--color-success);
    color: hsla(142, 70%, 45%, 0.4);
}

.solved-status-icon.solved {
    background-color: var(--color-success);
    border-color: var(--color-success);
    color: white;
}

/* Solved state on problem item row */
.problem-item.is-solved .problem-title {
    text-decoration: line-through;
    color: var(--text-muted);
}

/* Viewer active solved status state */
.btn-solved-active {
    background-color: var(--color-success) !important;
    border-color: var(--color-success) !important;
    color: white !important;
}