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

body {
    font-family: Arial, sans-serif;
    background-color: #eef3fb;
    color: #243b55;
    min-height: 100vh;
    padding: 30px;
}

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

header {
    text-align: center;
    margin-bottom: 35px;
}

header h1 {
    color: #1d4ed8;
    font-size: 36px;
    margin-bottom: 10px;
}

header p {
    color: #64748b;
    font-size: 16px;
}

.card {
    background-color: white;
    padding: 30px;
    border-radius: 12px;
    margin-bottom: 25px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
}

.card h2 {
    color: #243b55;
    font-size: 22px;
    margin-bottom: 25px;
}

#bookForm {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.form-group label {
    font-size: 14px;
    font-weight: bold;
    color: #334155;
}

input, select {
    width: 100%;
    padding: 12px;
    border: 1px solid #cbd5e1;
    border-radius: 7px;
    font-size: 14px;
    background: white;
}

input:focus, select:focus {
    outline: none;
    border-color: #2563eb;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

button {
    border: none;
    border-radius: 7px;
    padding: 12px 18px;
    color: white;
    font-size: 14px;
    font-weight: bold;
    cursor: pointer;
    transition: background-color 0.2s;
}

.add-btn {
    background-color: #2563eb;
    align-self: end;
}

.add-btn:hover {
    background-color: #1d4ed8;
}

.summary {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 25px;
    margin-bottom: 25px;
}

.summary-card {
    background-color: white;
    padding: 30px;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.08);
    border-left: 5px solid #2563eb;
}

.summary-card h3 {
    font-size: 17px;
    color: #64748b;
    margin-bottom: 15px;
}

.summary-card p {
    font-size: 38px;
    font-weight: bold;
    color: #2563eb;
}

.overdue-card {
    border-left-color: #dc2626;
}

.overdue-card p {
    color: #dc2626;
}

.table-container {
    width: 100%;
    overflow-x: auto;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 10px;
}

thead {
    background-color: #2563eb;
    color: white;
}

th {
    padding: 15px;
    text-align: left;
    font-size: 14px;
}

td {
    padding: 15px;
    border-bottom: 1px solid #e2e8f0;
    font-size: 14px;
}

tbody tr:nth-child(even) {
    background-color: #f8fafc;
}

tbody tr:hover {
    background-color: #eff6ff;
}

.active {
    color: #16a34a;
    font-weight: bold;
}

.overdue {
    color: #dc2626;
    font-weight: bold;
}

.returned {
    color: #64748b;
    font-weight: bold;
}

.return-btn {
    background-color: #16a34a;
    padding: 9px 12px;
    margin: 3px;
}

.return-btn:hover {
    background-color: #15803d;
}

.delete-btn {
    background-color: #dc2626;
    padding: 9px 12px;
    margin: 3px;
}

.delete-btn:hover {
    background-color: #b91c1c;
}

.empty-message {
    text-align: center;
    color: #64748b;
    padding: 25px;
}

@media (max-width: 800px) {
    #bookForm {
        grid-template-columns: 1fr 1fr;
    }
}

@media (max-width: 600px) {
    body {
        padding: 15px;
    }

    header h1 {
        font-size: 28px;
    }

    #bookForm {
        grid-template-columns: 1fr;
    }

    .summary {
        grid-template-columns: 1fr;
    }

    .card {
        padding: 20px;
    }
}