/* Global Styles */
:root {
    --primary-color: #4a6fa5;
    --secondary-color: #166088;
    --accent-color: #4fc3f7;
    --light-color: #f8f9fa;
    --dark-color: #212529;
    --success-color: #28a745;
    --error-color: #dc3545;
    --warning-color: #ffc107;
    --border-radius: 4px;
    --box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--dark-color);
    background-color: var(--light-color);
    padding: 0;
    margin: 0;
}

header {
    background-color: var(--primary-color);
    color: white;
    padding: 2rem 1rem;
    text-align: center;
    margin-bottom: 2rem;
}

header h1 {
    margin-bottom: 1rem;
    font-size: 2.5rem;
}

header p {
    font-size: 1.2rem;
    max-width: 800px;
    margin: 0 auto;
}

section {
    padding: 1.5rem;
    margin-bottom: 2rem;
    background-color: white;
    border-radius: var(--border-radius);
    box-shadow: var(--box-shadow);
    max-width: 1200px;
    margin-left: auto;
    margin-right: auto;
}

section h2 {
    color: var(--secondary-color);
    margin-bottom: 1.5rem;
    padding-bottom: 0.5rem;
    border-bottom: 2px solid var(--accent-color);
}

article {
    margin-bottom: 2rem;
}

article h2, article h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

/* Lists Section */
#lists {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

ul, ol {
    padding-left: 2rem;
    margin-bottom: 1rem;
}

li {
    margin-bottom: 0.5rem;
}

dl {
    display: grid;
    grid-template-columns: max-content auto;
    gap: 0.5rem 1rem;
}

dt {
    font-weight: bold;
    color: var(--secondary-color);
}

dd {
    margin-bottom: 0.5rem;
}

/* Tables Section */
table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: 1rem;
}

th, td {
    padding: 0.75rem;
    text-align: left;
    border: 1px solid #dee2e6;
}

th {
    background-color: var(--primary-color);
    color: white;
}

tr:nth-child(even) {
    background-color: #f2f2f2;
}

/* Media Section */
#media {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
}

figure {
    margin: 1rem 0;
    text-align: center;
}

img {
    max-width: 100%;
    height: auto;
    border-radius: var(--border-radius);
}

figcaption {
    margin-top: 0.5rem;
    font-style: italic;
    color: #666;
}

video, audio {
    width: 100%;
    border-radius: var(--border-radius);
}

/* Form Section */
form {
    display: grid;
    gap: 1.5rem;
}

fieldset {
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
    padding: 1.5rem;
    margin-bottom: 1rem;
}

legend {
    padding: 0 0.5rem;
    font-weight: bold;
    color: var(--secondary-color);
}

.form-row {
    margin-bottom: 1rem;
}

label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

input:not([type="checkbox"]):not([type="radio"]),
select, textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: var(--transition);
}

input:focus:not([type="checkbox"]):not([type="radio"]),
select:focus, textarea:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(74, 111, 165, 0.25);
}

input[type="checkbox"], input[type="radio"] {
    margin-right: 0.5rem;
}

.inline-label {
    display: inline;
    font-weight: normal;
}

button {
    padding: 0.75rem 1.5rem;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    font-size: 1rem;
    transition: var(--transition);
    margin-right: 1rem;
}

button:hover {
    background-color: var(--secondary-color);
}

button[type="reset"] {
    background-color: #6c757d;
}

button[type="reset"]:hover {
    background-color: #5a6268;
}

.required:after {
    content: " *";
    color: var(--error-color);
}

/* Footer */
footer {
    background-color: var(--dark-color);
    color: white;
    text-align: center;
    padding: 2rem 1rem;
    margin-top: 2rem;
}

footer a {
    color: var(--accent-color);
    text-decoration: none;
}

footer a:hover {
    text-decoration: underline;
}

/* Responsive Design */
@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }
    
    header p {
        font-size: 1rem;
    }
    
    section {
        padding: 1rem;
    }
    
    #lists {
        grid-template-columns: 1fr;
    }
    
    dl {
        grid-template-columns: 1fr;
    }
    
    dt {
        margin-top: 0.5rem;
    }
    
    .form-row {
        margin-bottom: 1.5rem;
    }
    
    button {
        width: 100%;
        margin-bottom: 1rem;
    }
}

@media (max-width: 480px) {
    header {
        padding: 1.5rem 1rem;
    }
    
    header h1 {
        font-size: 1.75rem;
    }
    
    fieldset {
        padding: 1rem;
    }
    
    th, td {
        padding: 0.5rem;
        font-size: 0.9rem;
    }
}

/* Form Validation Styles */
input:invalid, textarea:invalid {
    border-color: var(--error-color);
}

input:valid, textarea:valid {
    border-color: var(--success-color);
}

input:focus:invalid, textarea:focus:invalid {
    box-shadow: 0 0 0 3px rgba(220, 53, 69, 0.25);
}

.error-message {
    color: var(--error-color);
    font-size: 0.875rem;
    margin-top: 0.25rem;
    display: none;
}

input:invalid ~ .error-message,
textarea:invalid ~ .error-message {
    display: block;
}