:root {
    /* Color Palette - Light Mode */
    --bg-primary: #f8fafc;
    --bg-secondary: #ffffff;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    
    --accent-color: #3b82f6;
    --accent-hover: #2563eb;
    --accent-light: #eff6ff;
    
    --border-color: #e2e8f0;
    --border-focus: #93c5fd;
    
    --success: #10b981;
    --error: #ef4444;
    
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 20px;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
    
    --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

[data-theme="dark"] {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #0f172a;
    --text-primary: #f8fafc;
    --text-secondary: #cbd5e1;
    --text-muted: #64748b;
    
    --accent-color: #60a5fa;
    --accent-hover: #3b82f6;
    --accent-light: #1e3a8a;
    
    --border-color: #334155;
    --border-focus: #3b82f6;
    
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.3);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.5), 0 2px 4px -2px rgb(0 0 0 / 0.5);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.5), 0 4px 6px -4px rgb(0 0 0 / 0.5);
}

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

body {
    font-family: var(--font-sans);
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
    transition: background-color var(--transition), color var(--transition);
}

.app-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Header */
.header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 2rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.header h1 {
    font-size: 2rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--accent-color), #8b5cf6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    margin-bottom: 0.5rem;
}

.header p {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.btn-icon {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    width: 44px;
    height: 44px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
}

.btn-icon:hover {
    background: var(--bg-tertiary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.btn-icon svg {
    width: 20px;
    height: 20px;
}

/* Main Content Layout */
.main-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    flex: 1;
}

@media (max-width: 1024px) {
    .main-content {
        grid-template-columns: 1fr;
    }
}

/* Panels */
.panel {
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-md);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transition: var(--transition);
}

.panel:hover {
    box-shadow: var(--shadow-lg);
}

.panel-header {
    padding: 1.25rem 1.5rem;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: var(--bg-tertiary);
}

.panel-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.mt-4 {
    margin-top: 1rem;
    border-top: 1px solid var(--border-color);
}

/* XML Editor */
.editor-container {
    flex: 1;
    display: flex;
    min-height: 400px;
}

#xml-input {
    width: 100%;
    height: 100%;
    padding: 1.5rem;
    font-family: var(--font-mono);
    font-size: 0.95rem;
    line-height: 1.6;
    color: var(--text-primary);
    background: var(--bg-secondary);
    border: none;
    resize: none;
    outline: none;
}

/* Controls */
.select-modern {
    appearance: none;
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    padding: 0.5rem 2.5rem 0.5rem 1rem;
    border-radius: var(--radius-sm);
    font-family: var(--font-sans);
    font-size: 0.95rem;
    cursor: pointer;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 24 24' stroke='%2364748b'%3E%3Cpath stroke-linecap='round' stroke-linejoin='round' stroke-width='2' d='M19 9l-7 7-7-7'%3E%3C/path%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 0.75rem center;
    background-size: 1.25rem;
    transition: var(--transition);
}

.select-modern:focus {
    outline: none;
    border-color: var(--border-focus);
    box-shadow: 0 0 0 3px var(--accent-light);
}

/* Query Panel */
.exercises-container {
    padding: 1.5rem 1.5rem 0 1.5rem;
}

.full-width {
    width: 100%;
    margin-bottom: 1rem;
}

.exercise-details {
    background: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    padding: 1rem;
    margin-bottom: 1rem;
    border: 1px solid var(--border-color);
}

.exercise-details.hidden {
    display: none;
}

.exercise-header-flex {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 1rem;
    margin-bottom: 0.75rem;
}

.exercise-text {
    font-size: 0.95rem;
    color: var(--text-primary);
    font-weight: 500;
    margin-bottom: 0;
}

.exercise-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 0.5rem;
}

.btn-small {
    padding: 0.4rem 0.8rem;
    font-size: 0.85rem;
}

.btn-text {
    background: none;
    border: none;
    color: var(--accent-color);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    padding: 0;
}

.btn-text:hover {
    text-decoration: underline;
}

.solution-box {
    margin-top: 0.75rem;
    padding: 0.75rem;
    background: var(--bg-primary);
    border-left: 3px solid var(--success);
    font-family: var(--font-mono);
    font-size: 0.9rem;
    color: var(--success);
    border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
    word-break: break-all;
}

.solution-box.hidden {
    display: none;
}

.border-top {
    border-top: 1px solid var(--border-color);
    margin-top: 0.5rem;
}

.query-container {
    padding: 1.5rem;
}

.input-group-vertical {
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.input-field-wrapper {
    display: flex;
    align-items: center;
    background: var(--bg-primary);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 0.5rem;
    transition: var(--transition);
}

.input-field-wrapper:focus-within {
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px var(--accent-light);
}

.input-prefix {
    padding: 0 1rem;
    color: var(--accent-color);
    font-weight: 600;
    font-family: var(--font-mono);
    font-size: 1.2rem;
}

#xpath-input {
    flex: 1;
    background: transparent;
    border: none;
    padding: 0.75rem 0;
    font-family: var(--font-mono);
    font-size: 1.2rem;
    color: var(--text-primary);
    outline: none;
}

.btn-block {
    width: 100%;
    padding: 1rem;
    font-size: 1.1rem;
}

.btn-primary {
    background: var(--accent-color);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: var(--transition);
}

.btn-primary:hover {
    background: var(--accent-hover);
    transform: translateY(-1px);
}

.examples-list {
    margin-top: 1.25rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.75rem;
    align-items: center;
}

.examples-label {
    font-size: 0.9rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.example-btn {
    background: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 0.4rem 0.8rem;
    border-radius: 20px;
    font-size: 0.85rem;
    cursor: pointer;
    transition: var(--transition);
}

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

/* Result Area */
.result-container {
    flex: 1;
    padding: 0;
    background: var(--bg-primary);
    overflow-y: auto;
    position: relative;
    min-height: 250px;
}

#result-output {
    padding: 1.5rem;
    font-family: var(--font-mono);
    font-size: 0.95rem;
    line-height: 1.6;
    color: var(--text-primary);
    white-space: pre-wrap;
    word-break: break-all;
}

.badge {
    background: var(--bg-primary);
    color: var(--text-secondary);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 600;
    border: 1px solid var(--border-color);
}

.badge.success {
    background: #dcfce7;
    color: #166534;
    border-color: #bbf7d0;
}

[data-theme="dark"] .badge.success {
    background: rgba(16, 185, 129, 0.2);
    color: #34d399;
    border-color: rgba(16, 185, 129, 0.3);
}

.badge.error {
    background: #fee2e2;
    color: #991b1b;
    border-color: #fecaca;
}

[data-theme="dark"] .badge.error {
    background: rgba(239, 68, 68, 0.2);
    color: #f87171;
    border-color: rgba(239, 68, 68, 0.3);
}

/* Error state text */
.error-text {
    color: var(--error);
}

.footer {
    margin-top: 3rem;
    text-align: center;
    color: var(--text-muted);
    font-size: 0.9rem;
}

/* Highlight formatting for XML */
.xml-tag { color: #3b82f6; }
.xml-attr { color: #8b5cf6; }
.xml-val { color: #10b981; }
.xml-text { color: var(--text-primary); }

[data-theme="dark"] .xml-tag { color: #60a5fa; }
[data-theme="dark"] .xml-attr { color: #a78bfa; }
[data-theme="dark"] .xml-val { color: #34d399; }

/* Scrollbar */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}
::-webkit-scrollbar-track {
    background: var(--bg-primary);
}
::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: var(--text-muted);
}