* {
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Verdana, sans-serif;
    display: flex;
    background-color: #0B3861;
    margin: 0;
    padding: 0;
    position: relative;
    min-height: 100vh;
    flex-direction: column;
    align-items: center;
}

.header {
    position: sticky;
    display: flex;
    height: 60px;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    top: 0;
    z-index: 10;
    background-color: rgba(11, 56, 97, 0.9);
    backdrop-filter: blur(4px);
}

.logo {
    font-size: 1.5rem;
    font-weight: 600;
    color: #f0f0f0;
}

/* Bouton hamburger caché en PC */
.menu-toggle {
    display: none;
    font-size: 2rem;
    color: #f0f0f0;
    cursor: pointer;
}

.nav ul {
    display: flex;
    list-style-type: none;
    color: #f0f0f0;
    font-size: 1em;
    gap: 1rem;
}

.nav ul li a {
    text-decoration: none;
    color: #f0f0f0;
    border-radius: 5px;
    padding: 0.5rem 1rem;   
}

.nav ul li a:hover { /* tous liens lors du survol dans la balise nav */
    color: #ffde7d; /* couleur de fond */
}

.background-animation {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    overflow: hidden;
}

.circle {
    position: absolute;
    border-radius: 50%;
    animation: move 5s infinite ease-in-out;
    filter: blur(6px);
    mix-blend-mode: soft-light;
    pointer-events: none;
    z-index: 0;
}

@keyframes move {
    0%, 100% {
        transform: translate(0, 0);
    }
    50% {
        transform: translate(20px, 20px);
    }
}

.graph-container {
    max-width: 900px;
    margin: 2rem auto;
    padding: 2rem;
    background-color: #fdf4e3;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.08);
    border-radius: 16px;
    border-left: 8px solid #f19c65;
}

.graph-container h3 {
    text-align: justify;
    color: #004466;
}

.graph-title h1 {
    font-family: Arial, Helvetica, sans-serif;
    text-align: center;
    font-size: 2.5rem;
    line-height: 1.3;
    color: #004466;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.05);
    font-weight: 700;
    padding: 1rem;
    margin-bottom: 1rem;
}

.graph-title h1, h3 {
    opacity: 0;
    transform: translateY(20px);
    animation: fadeInUp 1s ease-out forwards;
}

@keyframes fadeInUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.graph-card {
    max-width: 800px;
    width: 95%;
    margin: 0 auto;
    padding-top: 20px;
    text-align: center;
}

.graph-title {
    text-align: center;
    margin-bottom: 20px;
}

.graph-content {
    line-height: 1.6rem;
    font-size: 1rem;
    text-align: justify;
}

.graph-content p {
    text-align: justify;
}

.graph-card img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 0 auto;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.graph-card img:hover {
    transform: scale(1.02);
    box-shadow: 0 8px 20px rgba(0, 0, 0, 0.2);
}

.button {
    border: none;
    border-radius: 5px;
    color: white;
    text-decoration: none;
    text-align: center;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

.button-retour {
    text-align: center;
    margin-top: 2rem;
}

.button-retour a {
    display: inline-block;
    background: transparent;
    color: #004466;
    border: 1px solid #004466;
    border-radius: 5px;
    text-decoration: none;
    font-size: 1rem;
    font-weight: 600;
    padding: 0.5rem 1.25rem;
    transition: all 0.3s ease;
}

.button-retour a:hover {
    background-color: #004466;
    color: white;
}

.footer {
    height: 100%;
    margin: 0;
    display: flex;
    background-color: #0B3861;
    color: white;
    padding: 2rem 1rem;
    margin-top: 4rem;
}

.footer-container {
    margin: 0 auto;
    text-align: center;
}

.footer a {
    color: white;
}

.footer a:hover {
    color: #ffcc70;
}

.footer-links {
    margin-top: 1rem;
}

.footer-links a {
    margin: 0 10px;
    color: white;
    text-decoration: none;
}

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

/* mobile */
@media(max-width: 768px) {
    .menu-toggle {
        display: flex;
    }
    .menu-toggle.open span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    .menu-toggle.open span:nth-child(2) {
        opacity: 0;
    }
    .menu-toggle.open span:nth-child(3) {
        transform: rotate(-45deg) translate(6px, -6px);
    }
    .menu-toggle span {
        transition: all 0.3s ease;
    }

    .nav ul {
        display: none;
        flex-direction: column;
        width: 100%;
        background: rgba(11, 56, 97, 0.95);
        padding: 1rem;
        margin: 0;
        text-align: left;
    }
    .nav.active ul {
        display: flex;
    }
    .nav ul li {
        margin: 0.5rem 0;
        text-align: left;
    }

    .nav ul li a{
        color: #fff;
        display: block;
        width: 100%;
    }
    .graph-container {
        grid-template-columns: 1fr;
        gap: 1rem;
        padding: 1rem;
    }
    .graph-title h1 {
        font-size: 1.8rem;  /* 28-30px */
    }
    .graph-content {
        padding: 0 0.5rem;
    }
    .graph-content p {
        font-size: 0.95rem;
        line-height: 1.6;
    }
    .button-retour a {
        font-size: 0.9rem;
        padding: 0.4rem 1rem;
    }

    .footer {
        flex-direction: column;
        padding: 1.5rem 1rem;
    }

    .footer-links {
        margin-top: 1rem;
        display: flex;
        flex-direction: column;
        gap: 0.5rem;
    }

    .footer-links a {
        margin: 0;
    }
}