:root {
    --primary-color: #3498db;
    --secondary-color: #2c3e50;
    --accent-color: #e74c3c;
    --light-color: #ecf0f1;
    --dark-color: #2c3e50;
    --success-color: #2ecc71;
    --warning-color: #f39c12;
    --card-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
    --border-radius: 12px;
    --font-primary: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: var(--font-primary);
}

body {
    background-image: linear-gradient(to top, #0ba360 0%, #3cba92 100%);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    padding: 20px;
    color: var(--light-color);
}

.calculator-container {
    width: 100%;
    max-width: 800px;
    text-align: center;
    padding: 2rem;
    background: rgba(255, 255, 255, 0.1);
    border-radius: var(--border-radius);
    box-shadow: var(--card-shadow);
    backdrop-filter: blur(10px);
    margin: auto; /* Center the container vertically */
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 0.5rem;
    color: var(--light-color);
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

header p {
    color: var(--light-color);
    opacity: 0.9;
    margin-bottom: 2rem;
}

.calculator-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 1.5rem;
}

@media (min-width: 769px) {
    .calculator-grid {
        grid-template-columns: 1fr 1fr; /* Two columns on larger screens */
    }
}

.calculator-card {
    background: rgba(44, 62, 80, 0.7); /* Darker card background */
    border-radius: var(--border-radius);
    padding: 1.5rem;
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    transition: var(--transition);
    border-top: 1px solid rgba(255, 255, 255, 0.2);
    border-left: 1px solid rgba(255, 255, 255, 0.2);
}

.calculator-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
}

.calculator-card h3 {
    color: var(--light-color);
    margin-bottom: 1rem;
    font-size: 1.4rem;
}

.input-group {
    margin-bottom: 1rem;
    text-align: left;
}

.input-group label {
    display: block;
    margin-bottom: 0.5rem;
    color: var(--light-color);
    font-weight: 500;
}

.input-group input,
.input-group select {
    width: 100%;
    padding: 0.8rem;
    border: 1px solid #7f8c8d;
    background-color: #ecf0f1;
    color: var(--secondary-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
}

button {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: var(--transition);
    width: 100%;
    margin-top: 0.5rem;
}

button:hover {
    background: #2980b9;
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(52, 152, 219, 0.3);
}

.result {
    margin-top: 1rem;
    padding: 1rem;
    background: rgba(0, 0, 0, 0.2);
    border-radius: var(--border-radius);
    font-weight: 600;
    color: var(--light-color);
    text-align: center;
    display: block;
    word-wrap: break-word;
    font-size: 1.8rem;
    font-weight: bold;
}

/* Specific styles for GWA calculator */
.course-inputs-container {
    margin-bottom: 1.5rem;
}

.course-row {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
    align-items: center;
    justify-content: center;
}

.course-row input {
    flex: 1;
    padding: 0.8rem;
    border: 1px solid #7f8c8d;
    background-color: #ecf0f1;
    color: var(--secondary-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    min-width: 0; /* Allow flex item to shrink below content size */
}

.course-row button.remove-course-btn {
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 8px;
    padding: 0.8rem;
    cursor: pointer;
    font-size: 1rem;
    transition: var(--transition);
    width: auto;
    margin-top: 0;
}

.course-row button.remove-course-btn:hover {
    background-color: #c0392b;
    transform: translateY(-2px);
    box-shadow: 0 4px 10px rgba(231, 76, 60, 0.3);
}

#add-course-btn,
#calculate-gwa-btn {
    width: auto;
    display: inline-block;
    margin: 0.5rem;
    padding: 0.8rem 1.5rem;
}

#calculate-gwa-btn {
    background-color: var(--success-color);
}

#calculate-gwa-btn:hover {
    background-color: #27ae60;
    box-shadow: 0 4px 10px rgba(46, 204, 113, 0.3);
}

/* History Section */
#history-container {
    margin: 1rem 0;
}

#no-history-message {
    color: #bdc3c7;
    font-style: italic;
    margin: 1rem 0;
}

.history-item {
    background: rgba(0, 0, 0, 0.2);
    padding: 0.8rem;
    margin: 0.5rem 0;
    border-radius: 8px;
    border-left: 3px solid var(--primary-color);
}

.history-item-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.5rem;
}

.history-item-title {
    font-weight: bold;
    color: var(--light-color);
}

.history-item-timestamp {
    font-size: 0.8rem;
    color: #bdc3c7;
}

.history-item-courses {
    margin: 0.5rem 0;
}

.history-item-course {
    display: flex;
    justify-content: space-between;
    padding: 0.2rem 0;
    border-bottom: 1px dashed rgba(255, 255, 255, 0.1);
}

.history-item-course:last-child {
    border-bottom: none;
}

.history-item-course-grade,
.history-item-course-units {
    color: var(--light-color);
    font-weight: 500;
}

.history-item-gwa {
    margin-top: 0.5rem;
    padding-top: 0.5rem;
    border-top: 1px solid rgba(255, 255, 255, 0.2);
    font-weight: bold;
    color: var(--success-color);
    text-align: center;
}

.history-actions {
    display: flex;
    gap: 0.5rem;
    margin-top: 0.8rem;
}

.history-btn {
    flex: 1;
    margin-top: 0;
    padding: 0.5rem;
    font-size: 0.9rem;
}

.load-history-btn {
    background-color: var(--primary-color);
}

.load-history-btn:hover {
    background-color: #2980b9;
}

.delete-history-btn {
    background-color: var(--accent-color);
}

.delete-history-btn:hover {
    background-color: #c0392b;
}

#clear-history-btn {
    background-color: var(--warning-color);
    width: 100%;
    margin-top: 1rem;
}

#clear-history-btn:hover {
    background-color: #e67e22;
}

#add-course-btn,
#calculate-gwa-btn {
    width: 100%;
    margin: 0.5rem 0;
}

.back-link {
    display: inline-block;
    margin-bottom: 1.5rem;
    margin-top: 1rem; /* Adjust as needed */
    padding: 0.8rem 1.5rem;
    background-color: var(--primary-color);
    color: white;
    text-decoration: none;
    border-radius: 25px;
    transition: var(--transition);
    font-weight: 600;
}

.back-link:hover {
    background-color: #2980b9;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(52, 152, 219, 0.4);
}

@media (max-width: 768px) {
    .calculator-container {
        padding: 1rem;
    }

    header h1 {
        font-size: 2rem;
    }

    .course-row {
        flex-direction: column;
        align-items: stretch;
    }

    .course-row input,
    .course-row button.remove-course-btn {
        width: 100%;
        margin: 0.25rem 0;
    }

    #add-course-btn,
    #calculate-gwa-btn {
        width: 100%;
        margin: 0.5rem 0;
    }
}

/* Footer */
footer {
    margin-top: 3rem;
    padding: 2rem 0;
    text-align: center;
    color: white;
    opacity: 0.8;
    font-size: 0.9rem;
    border-top: 1px solid rgba(255, 255, 255, 0.2);
}

.footer-content {
    display: flex;
    justify-content: center;
    text-align: center;
    align-items: center;
    flex-wrap: wrap;
    gap: 2rem;
}

.footer-left h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
    font-weight: 700;
}

.footer-left p {
    font-size: 0.9rem;
    opacity: 0.8;
}