/* Reset and Base Styles */
body {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    background-color: #f8f9fa; /* Light gray background */
    margin: 0;
    padding: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

/* Layout Utilities */
.main-content {
    flex: 1; /* Forces footer down if content is short */
}

/* Header Styling */
header {
    background-color: #212529; /* Bootstrap Dark */
    color: white;
    padding-top: 3rem;
    padding-bottom: 3rem;
    border-bottom: 5px solid #0d6efd; /* Accent line */
}

header h1 {
    font-weight: 800;
    letter-spacing: -0.5px;
}

/* Grid Container Styling */
.main-content .container {
    padding-top: 3rem;
    padding-bottom: 3rem;
}

/* Button Card Container */
.chart-btn {
    /* Layout properties */
    height: 160px; /* Slightly taller for comfort */
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    
    /* Visual properties */
    border: none;
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
    
    /* Link styling inside button */
    text-decoration: none;
    color: inherit;
    width: 100%;
}

/* Button Hover Effects */
.chart-btn:hover {
    transform: translateY(-8px);
    box-shadow: 0 12px 20px rgba(0, 0, 0, 0.15);
}

/* Button Content Styling */
.chart-btn .btn-title {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    display: block;
}

.chart-btn .btn-subtitle {
    font-size: 0.875rem;
    opacity: 0.8;
    font-weight: 500;
}

/* Color Variants */
.btn-variant-1 {
    background-color: #0d6efd; /* Blue */
    color: white;
}
.btn-variant-1:hover {
    background-color: #0b5ed7;
}

.btn-variant-2 {
    background-color: #198754; /* Green */
    color: white;
}
.btn-variant-2:hover {
    background-color: #157347;
}

.btn-variant-3 {
    background-color: #dc3545; /* Red */
    color: white;
}
.btn-variant-3:hover {
    background-color: #b02a37;
}

.btn-variant-4 {
    background-color: #6c757d; /* Grey */
    color: white;
}
.btn-variant-4:hover {
    background-color: #5a6268;
}

/* Footer Styling */
footer {
    background-color: #212529;
    color: rgba(255,255,255,0.6);
    padding-top: 2rem;
    padding-bottom: 2rem;
    font-size: 0.9rem;
    border-top: 1px solid #383f45;
}