:root {
    --primary-color: #0b3f24; /* Deep emerald green */
    --accent-color: #d4af37; /* Gold */
    --bg-color: #f5f6f5;
    --card-bg: #ffffff;
    --text-color: #2c3e50;
    --text-muted: #7f8c8d;
}

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

body {
    font-family: 'Outfit', sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

.navbar {
    background-color: var(--primary-color);
    padding: 20px 40px;
    box-shadow: 0 4px 15px rgba(0,0,0,0.1);
}

.logo {
    color: var(--accent-color);
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: 1px;
    text-transform: uppercase;
}

.container {
    max-width: 1200px;
    margin: 60px auto;
    padding: 0 20px;
}

.book-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 30px;
}

.product-card {
    background-color: var(--card-bg);
    border-radius: 16px;
    overflow: hidden;
    box-shadow: 0 10px 30px rgba(0,0,0,0.05);
    display: flex;
    flex-direction: column;
    transition: transform 0.3s ease;
}

.product-card:hover {
    transform: translateY(-5px);
}

.product-image {
    background-color: #eef2f0;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 30px;
    height: 300px;
}

.product-image img {
    max-height: 100%;
    width: auto;
    border-radius: 8px;
    box-shadow: 0 10px 25px rgba(0,0,0,0.15);
}

.product-details {
    padding: 30px 25px;
    display: flex;
    flex-direction: column;
    flex-grow: 1;
}

.product-title {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 10px;
    font-weight: 700;
}

.product-description {
    color: var(--text-muted);
    font-size: 0.95rem;
    margin-bottom: 15px;
    flex-grow: 1;
}

.product-price {
    font-size: 2rem;
    font-weight: 700;
    color: var(--accent-color);
    margin-bottom: 20px;
}

.product-price span {
    font-size: 1rem;
    color: var(--text-muted);
    font-weight: 400;
}

.checkout-form {
    background-color: #f9faf9;
    padding: 20px;
    border-radius: 12px;
    border: 1px solid #e1e8e4;
    margin-top: auto;
}

.input-group {
    margin-bottom: 15px;
}

.input-group input {
    width: 100%;
    padding: 10px 15px;
    border: 1px solid #cbd5cf;
    border-radius: 8px;
    font-family: inherit;
    font-size: 0.95rem;
    transition: all 0.3s ease;
}

.input-group input:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(212, 175, 55, 0.2);
}

.btn-buy {
    background-color: var(--primary-color);
    color: var(--accent-color);
    border: none;
    padding: 12px 20px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: 8px;
    cursor: pointer;
    width: 100%;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.btn-buy:hover {
    background-color: #082d1a;
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(11, 63, 36, 0.2);
}

.error-msg {
    background-color: #ffeaea;
    color: #d63031;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 30px;
    font-weight: 600;
    border-left: 4px solid #d63031;
}