/* ===== CSS CUSTOM PROPERTIES ===== */
:root {
    /* Background Colors */
    --bg-main: #f1f3f4;
    --bg-editor-pane: #f8f9fa;
    --bg-preview-pane: #e8eaed;
    --bg-preview-container: #dadce0;
    --bg-page: #ffffff;
    --bg-primary: #4774ae;
    --bg-primary-hover: #2f68b3;
    --bg-primary-active: #1346a0;
    
    /* Text Colors */
    --text-primary: #3c4043;
    --text-secondary: #5f6368;
    --text-white: #ffffff;
    --text-danger: #d93025;
    --text-warning: #f57c00;
    --text-success: #137333;
    --text-info: #1a73e8;
    
    /* Border Colors */
    --border-light: #c1c7cd;
    --border-medium: #dadce0;
    --border-dashed: #9aa0a6;
    --border-danger: #ea4335;
    --border-warning: #fbbc04;
    --border-success: #34a853;
    --border-info: #4285f4;
    --border-focus: #1a73e8;
    
    /* Alert Background Colors */
    --bg-alert-danger: #fce8e6;
    --bg-alert-warning: #fef7e0;
    --bg-alert-success: #e6f4ea;
    --bg-alert-info: #e8f0fe;
    
    /* Font Families */
    --font-system: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    --font-mono: 'Monaco', 'Menlo', 'Ubuntu Mono', monospace;
    
    /* Shadows */
    --shadow-page: 0 2px 8px rgba(60, 64, 67, 0.15);
    --shadow-focus: 0 0 0 2px rgba(26, 115, 232, 0.2);
    --shadow-focus-strong: 0 0 0 2px rgba(26, 115, 232, 0.3);
    
    /* Dimensions */
    --page-width: 21cm;
    --page-height: 29.7cm;
    --page-margin: 2cm;
    --border-radius: 4px;
    
    /* Spacing */
    --spacing-xs: 8px;
    --spacing-sm: 12px;
    --spacing-md: 16px;
    --spacing-lg: 20px;
    --spacing-xl: 24px;
    --spacing-2xl: 1.5rem;
}

/* ===== CSS RESET & BASE STYLES ===== */
* {
    box-sizing: border-box;
}

body { 
    background-color: var(--bg-main);
    margin: 0;
    padding: 0;
    font-family: var(--font-system);
}

/* ===== LAYOUT STRUCTURE ===== */
.main-container {
    display: flex;
    height: 100vh;
}

/* ===== EDITOR PANE ===== */
.editor-pane {
    height: 100vh;
    overflow: hidden; /* Prevent parent from scrolling */
    padding: 0;
    border-right: 1px solid var(--border-light);
    background-color: var(--bg-editor-pane);
    display: flex;
    flex-direction: column;
    flex-grow: 1;
    flex-basis: 50%; /* Initial width */
}

.editor-form {
    flex-grow: 1; /* Key to make it fill space */
    min-height: 0; /* Key for child scrolling */
    display: flex;
    flex-direction: column;
    padding: var(--spacing-md) var(--spacing-xl) var(--spacing-xl) var(--spacing-xl);
}

.markdown-textarea-wrapper {
    flex-grow: 1;
    min-height: 0; /* allows textarea to scroll */
    display: flex;
    flex-direction: column;
}

/* ===== PREVIEW PANE ===== */
.preview-pane {
    height: 100vh;
    overflow-y: hidden;
    padding: 0;
    background-color: var(--bg-preview-pane);
    position: relative;
    display: flex;
    flex-direction: column;
    flex-grow: 1;
    flex-basis: 50%; /* Initial width */
}

.preview-container {
    background: var(--bg-preview-container);
    flex-grow: 1;
    overflow-y: auto;
    padding: var(--spacing-lg);
    position: relative;
    min-height: initial; /* Override min-height: 100% */
}

.preview-page {
    background: var(--bg-page);
    box-shadow: var(--shadow-page);
    margin: 0 auto var(--spacing-lg) auto;
    position: relative;
    width: var(--page-width);
    min-height: var(--page-height);
    max-width: 100%;
    border: 1px solid var(--border-medium);
}

.preview-page::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    border: 1px dashed var(--border-dashed);
    margin: var(--page-margin);
    pointer-events: none;
    z-index: 1;
}

.preview-content-area {
    padding: var(--page-margin);
    position: relative;
    z-index: 2;
    min-height: calc(var(--page-height) - calc(var(--page-margin) * 2));
}

/* ===== HEADERS ===== */
.pane-header {
    background-color: #e8eaed;
    border-bottom: 1px solid var(--border-light);
    padding: var(--spacing-sm) var(--spacing-xl);
    flex-shrink: 0;
}

.pane-header h4 {
    margin: 0;
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* ===== FORM ELEMENTS ===== */
.markdown-textarea-wrapper textarea {
    flex-grow: 1; /* Make textarea fill the wrapper */
    min-height: 150px;
    font-family: var(--font-mono);
    resize: none;
    background-color: var(--bg-page);
    border: 1px solid var(--border-light);
    border-radius: var(--border-radius);
    padding: var(--spacing-sm);
    font-size: 14px;
    line-height: 1.4;
}

.markdown-textarea-wrapper textarea:focus {
    border-color: var(--border-focus);
    outline: none;
    box-shadow: var(--shadow-focus);
}

.form-label {
    color: var(--text-primary);
    font-weight: 500;
    margin-bottom: var(--spacing-xs);
}

.form-control {
    border: 1px solid var(--border-light);
    border-radius: var(--border-radius);
    padding: var(--spacing-xs) var(--spacing-sm);
    background-color: var(--bg-page);
    color: var(--text-primary);
}

.form-control:focus {
    border-color: var(--border-focus);
    outline: none;
    box-shadow: var(--shadow-focus);
}

.form-select {
    border: 1px solid var(--border-light);
    border-radius: var(--border-radius);
    padding: var(--spacing-xs) var(--spacing-sm);
    background-color: var(--bg-page);
    color: var(--text-primary);
}

.form-select:focus {
    border-color: var(--border-focus);
    outline: none;
    box-shadow: var(--shadow-focus);
}

.form-text {
    color: var(--text-secondary);
    font-size: 0.875rem;
}

/* ===== BUTTONS ===== */
.btn-primary {
    background-color: var(--bg-primary);
    border-color: var(--bg-primary);
    color: var(--text-white);
    font-weight: 500;
    padding: var(--spacing-sm) var(--spacing-xl);
    border-radius: var(--border-radius);
    border: none;
}

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

.btn-primary:focus {
    background-color: var(--bg-primary-hover);
    border-color: var(--bg-primary-hover);
    box-shadow: var(--shadow-focus-strong);
}

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

/* ===== ALERTS ===== */
.alerts-wrapper {
    padding: var(--spacing-xl) var(--spacing-xl) 0;
}

.alerts-wrapper .alert:last-child {
    margin-bottom: 0;
}

.alert {
    border-radius: var(--border-radius);
    border: none;
    padding: var(--spacing-sm) var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.alert-danger {
    background-color: var(--bg-alert-danger);
    color: var(--text-danger);
    border-left: 4px solid var(--border-danger);
}

.alert-warning {
    background-color: var(--bg-alert-warning);
    color: var(--text-warning);
    border-left: 4px solid var(--border-warning);
}

.alert-success {
    background-color: var(--bg-alert-success);
    color: var(--text-success);
    border-left: 4px solid var(--border-success);
}

.alert-info {
    background-color: var(--bg-alert-info);
    color: var(--text-info);
    border-left: 4px solid var(--border-info);
}

/* ===== UTILITY CLASSES ===== */
.mb-3 {
    margin-bottom: 1rem;
}

.d-grid {
    display: grid;
}

.text-center {
    text-align: center;
}

hr {
    border: none;
    height: 1px;
    background-color: var(--border-medium);
    margin: var(--spacing-2xl) 0;
}

/* ===== RESIZER HANDLE ===== */
.resizer {
    flex-basis: 8px;
    flex-shrink: 0;
    background-color: var(--bg-preview-pane);
    cursor: col-resize;
    z-index: 10;
}
.resizer:hover {
    background-color: var(--border-light);
}