:root {
    --primary-color: #0d1b2a;
    --secondary-color: #ffffff;
    --button-bg: black;
    --button-hover: #333;
    --font-main: "Open Sans", sans-serif;
    --font-size-large: 1.5rem;
    --spacing-medium: 20px;
    --shadow: 0 4px 8px rgba(0, 0, 0, 0.2);
}

* {
    margin: 0;
    padding: 0;
    list-style-type: none;
    text-decoration: none;
}

html, body {
    height: 100%;
}

body {
    background-color: black;
    font-family: var(--font-main);
    text-align: center;
    color: var(--secondary-color);
}

.nav-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 40px;
    background-color: var(--primary-color);
    color: var(--secondary-color);
}

.nav-link {
    display: flex;
    align-items: center;
    gap: 30px;
}
.nav-link li a:visited {
    color: white;
}

.nav-bar li a:active {
    background-color: #0d1b2a;
    color: #ccc;
}

.nav-bar li button, .present-img button {
    border-radius: 10px;
    color: white;
    border: none;
    background-color: var(--button-bg);
    padding: 10px;
    transition: background-color 0.3s ease;
}

.nav-bar li button:hover, .present-img button:hover {
    background-color: var(--button-hover);
}

.present-img {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    font-size: var(--font-size-large);
    color: black;
    height: 100vh;
    background-image: url("../images/airplane-with-blur.png");
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;
}

.present-img * {
    padding: var(--spacing-medium);
}

.present-img button a:active {
    color: #ccc;
}

.present-img button a:visited {
    color: white;
}

/* Responsive */
@media (max-width: 768px) {
    .nav-bar {
        flex-direction: column;
        gap: 10px;
    }
}
footer {
    text-align: center;
    padding: 20px;
    background-color: var(--primary-color);
    color: white;
}