@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;600&display=swap');

:root {
    --bg-liquid: linear-gradient(135deg, #001f3f 0%, #0074D9 100%);
    --bg-solid: #ffffff;
    --bg-gas: linear-gradient(to top, #cfd9df 0%, #e2ebf0 100%);
    
    --text-main: #ffffff;

    --accent-solid: #00FFFF;
    --transition-speed: 0.5s;
}

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

body {
    font-family: 'Inter', sans-serif;
    min-height: 100vh;
    overflow-y: auto;
    transition: background var(--transition-speed) ease, color var(--transition-speed) ease;
    color: var(--text-main);
    text-shadow: 0 2px 4px rgba(0,0,0,0.6);
}

#app {
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    padding: 0;
}

/* Header & Nav */
header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    position: absolute;
    width: 100%;
    max-width: 900px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 10;
}

.brand {
    font-weight: 600;
    font-size: 1.5rem;
    letter-spacing: -1px;
    text-transform: uppercase;
}

nav a {
    text-decoration: none;
    margin-left: 0.5rem;
    font-size: 0.9rem;
    opacity: 0.6;
    cursor: pointer;
    transition: all 0.3s ease;
    color: inherit;
    padding: 0.5rem 1rem;
    border-radius: 50px;
}

nav a:hover, nav a.active {
    opacity: 1;
    text-decoration: none;
    background: rgba(255, 255, 255, 0.2);
}

/* Main Content */
#viewport {
    flex: 1 0 auto;
    width: 100%;
}

.photo-section {
    width: 100%;
    height: 50vh;
    background-size: cover;
    background-position: center;
    background-attachment: fixed;
    margin: 0;
}

.text-section {
    max-width: 900px;
    margin: 0 auto;
    padding: 4rem 2rem;
    animation: fadeIn 1.2s ease;
}

h1 {
    font-size: 3rem;
    font-weight: 300;
    margin-bottom: 1rem;
    line-height: 1.1;
}

.description {
    font-size: 1.1rem;
    line-height: 1.6;
    margin-bottom: 2rem;
    max-width: 600px;
}

.info-source {
    color: #ff8a80;
    text-decoration: none;
}

h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-top: 1.5rem;
    margin-bottom: 0.5rem;
}

p {
    margin-bottom: 1rem;
    line-height: 1.5;
    max-width: 600px;
}

/* Footer */
footer {
    font-size: 0.8rem;
    opacity: 0.7;
    text-align: center;
    padding: 2rem;
    width: 100%;
    max-width: 900px;
    margin: 0 auto;
}

.footer-logo-container {
    display: flex;
    justify-content: center;
    gap: 2.5rem;
    margin-bottom: 1rem;
}

.footer-logo-container img {
    width: 40px;
    height: 40px;
    object-fit: contain;
    transition: transform 0.3s ease;
}

.footer-logo-container img:hover {
    transform: scale(1.1);
}

/* Themes */
/* Page 1: Liquid */
body.page-0 {
    background: var(--bg-liquid);
}

/* Page 2: Solid */
body.page-1 {
    background: var(--bg-liquid);
}

body.page-1::before {
    content: '';
    position: absolute;
    top: -10%;
    right: -10%;
    width: 50vh;
    height: 50vh;
    background: var(--accent-solid);
    opacity: 0.1;
    transform: rotate(45deg);
    z-index: -1;
}

/* Page 3: Gas */
body.page-2 {
    background: var(--bg-liquid);
}

body.page-2 nav a {
    color: #000000;
    background-color: #b5cce0;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Mobile Responsive */
@media (max-width: 600px) {
    h1 { font-size: 2rem; }
    header { flex-direction: column; align-items: center; gap: 1rem; }
    nav { width: 100%; display: flex; flex-direction: column; gap: 0.5rem; }
    nav a { margin: 0; width: 100%; text-align: center; }
    .text-section { padding: 2rem 1.5rem; }
}