/* General Theme & Variables */
:root {
    --primary-color: #2563eb; /* blue-600 */
    --primary-hover: #1d4ed8; /* blue-700 */
    --secondary-color: #6b7280; /* gray-500 */
    --background-color: #f3f4f6; /* gray-100 */
    --card-background: #ffffff;
    --text-primary: #1f2937; /* gray-800 */
    --text-secondary: #4b5563; /* gray-600 */
    --border-color: #d1d5db; /* gray-300 */
    --success-color: #16a34a; /* green-600 */
    --error-color: #dc2626; /* red-600 */
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--background-color);
    color: var(--text-primary);
    margin: 0;
    padding: 20px;
    display: flex;
    flex-direction: column;
    align-items: center;
    min-height: 100vh;
}

.container {
    width: 100%;
    max-width: 960px;
    background-color: var(--card-background);
    padding: 30px;
    border-radius: 16px;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.1);
    margin-top: 20px;
}

h1, h2, h3 {
    color: var(--text-primary);
    text-align: center;
    margin-bottom: 1rem;
}

h1 { font-size: 2.25rem; font-weight: 700; }
h2 { font-size: 1.75rem; font-weight: 600; }
h3 { font-size: 1.25rem; font-weight: 600; }

p {
    color: var(--text-secondary);
    line-height: 1.6;
    text-align: center;
    margin-bottom: 1.5rem;
}

/* Card Layout for Index Pages */
.card-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 25px;
    margin-top: 2rem;
}

.card {
    background-color: #fff;
    border: 1px solid var(--border-color);
    border-radius: 12px;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.05);
    transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
    text-align: center;
    padding: 25px;
    display: flex;
    flex-direction: column;
}

/* Default hover effect for all cards */
.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.07);
    border-color: var(--primary-color);
}

.card:hover h3 {
    color: var(--primary-color);
}

.card-icon {
    font-size: 2.5rem; /* 40px */
    margin-bottom: 1rem;
    color: var(--primary-color);
    transition: color 0.3s ease;
}

.card:hover a {
    background-color: var(--primary-color);
    color: white;
}

.card h3 {
    margin-top: 0;
    transition: color 0.3s ease;
}

.card p {
    flex-grow: 1;
    margin-bottom: 1rem;
}

.card a {
    display: inline-block;
    text-decoration: none;
    color: var(--text-primary);
    background-color: var(--background-color);
    font-size: 1rem;
    font-weight: 600;
    padding: 10px 20px;
    border-radius: 8px;
    transition: background-color 0.3s ease, color 0.3s ease;
    margin-top: auto;
}

/* Buttons */
.btn {
    display: inline-block;
    font-weight: 600;
    padding: 12px 24px;
    border-radius: 8px;
    cursor: pointer;
    text-align: center;
    text-decoration: none;
    transition: all 0.2s ease;
    border: none;
}

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

.btn-secondary {
    background-color: var(--secondary-color);
    color: white;
}
.btn-secondary:hover {
    background-color: #4b5563; /* gray-600 */
}

/* Forms */
.form-input {
    width: 100%;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}
.form-input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

/* Back Link */
.back-link {
    display: inline-block;
    margin-bottom: 20px;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 600;
}
.back-link:hover {
    text-decoration: underline;
}

/* --- Individual Card Hover Colors (Home Page Only) --- */

/* 1. Rechnen lernen */
.home-page .card-container .card:nth-child(1):hover {
    border-color: #4a90e2;
}
.home-page .card-container .card:nth-child(1):hover .card-icon {
    color: #4a90e2;
}
.home-page .card-container .card:nth-child(1):hover h3 {
    color: #4a90e2;
}
.home-page .card-container .card:nth-child(1):hover a {
    background-color: #4a90e2;
    color: white;
}

/* 2. Finanzmathematik */
.home-page .card-container .card:nth-child(2):hover {
    border-color: #50e3c2;
}
.home-page .card-container .card:nth-child(2):hover .card-icon {
    color: #50e3c2;
}
.home-page .card-container .card:nth-child(2):hover h3 {
    color: #50e3c2;
}
.home-page .card-container .card:nth-child(2):hover a {
    background-color: #50e3c2;
    color: white;
}

/* 3. Lineare Funktionen */
.home-page .card-container .card:nth-child(3):hover {
    border-color: #f5a623;
}
.home-page .card-container .card:nth-child(3):hover .card-icon {
    color: #f5a623;
}
.home-page .card-container .card:nth-child(3):hover h3 {
    color: #f5a623;
}
.home-page .card-container .card:nth-child(3):hover a {
    background-color: #f5a623;
    color: white;
}

/* 4. Quadratische Funktionen */
.home-page .card-container .card:nth-child(4):hover {
    border-color: #bd10e0;
}
.home-page .card-container .card:nth-child(4):hover .card-icon {
    color: #bd10e0;
}
.home-page .card-container .card:nth-child(4):hover h3 {
    color: #bd10e0;
}
.home-page .card-container .card:nth-child(4):hover a {
    background-color: #bd10e0;
    color: white;
}

/* 5. Daten und Zufall */
.home-page .card-container .card:nth-child(5):hover {
    border-color: #7ed321;
}
.home-page .card-container .card:nth-child(5):hover .card-icon {
    color: #7ed321;
}
.home-page .card-container .card:nth-child(5):hover h3 {
    color: #7ed321;
}
.home-page .card-container .card:nth-child(5):hover a {
    background-color: #7ed321;
    color: white;
}

/* 6. Trigonometrie */
.home-page .card-container .card:nth-child(6):hover {
    border-color: #e02020;
}
.home-page .card-container .card:nth-child(6):hover .card-icon {
    color: #e02020;
}
.home-page .card-container .card:nth-child(6):hover h3 {
    color: #e02020;
}
.home-page .card-container .card:nth-child(6):hover a {
    background-color: #e02020;
    color: white;
}

footer {
    text-align: center;
    margin-top: 2rem;
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}