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

/* ===============================
   THEME SYSTEM
================================ */
:root {
    /* LIGHT MODE - BIRU MUDA */
    --bg-main: #e0f2fe;
    --bg-nav: #bae6fd;
    --bg-card: #ffffff;
    --bg-hero: linear-gradient(135deg, #38bdf8, #0ea5e9);
    --bg-footer: #7dd3fc;

    --text-main: #075985;
    --text-dark: #0c4a6e;

    --btn-bg: #0ea5e9;
    --btn-hover: #0284c7;
}

body.dark-mode {
    /* DARK MODE - BIRU TUA */
    --bg-main: #0f172a;
    --bg-nav: #1e293b;
    --bg-card: #1e3a8a;
    --bg-hero: linear-gradient(135deg, #1e3a8a, #172554);
    --bg-footer: #172554;

    --text-main: #e0f2fe;
    --text-dark: #ffffff;

    --btn-bg: #3b82f6;
    --btn-hover: #2563eb;
}

/* ===============================
   BODY
================================ */
body {
    font-family: Arial, Helvetica, sans-serif;
    background-color: var(--bg-main);
    color: var(--text-main);
    line-height: 1.7;
    transition: 0.3s ease;
}

/* ===============================
   NAVBAR
================================ */
nav {
    position: sticky;
    top: 0;
    z-index: 1000;

    display: flex;
    justify-content: space-between; /* tetap gunakan space-between */
    align-items: center;

    padding: 18px 8%;
    background: var(--bg-nav);
    box-shadow: 0 4px 15px rgba(0,0,0,0.15);
}

/* Flex container untuk menu & toggle button */
.nav-right {
    display: flex;
    align-items: center;
    gap: 20px; /* jarak antar link dan tombol */
}

nav .logo {
    font-size: 22px;
    font-weight: 700;
    color: var(--text-dark);
    transition: 0.3s;
}

nav .logo:hover {
    color: var(--btn-bg);
}

nav .nav-links a {
    position: relative;
    text-decoration: none;
    margin-left: 30px;
    color: var(--text-dark);
    font-weight: 500;
    transition: 0.3s;
}

nav .nav-links a:hover {
    color: var(--btn-bg);
}

nav .nav-links a::after {
    content: "";
    position: absolute;
    width: 0%;
    height: 2px;
    left: 0;
    bottom: -6px;
    background-color: var(--btn-bg);
    transition: 0.3s;
}

nav .nav-links a:hover::after {
    width: 100%;
}

/* DARK MODE BUTTON */
#darkModeToggle {
    margin-left: 25px;
    padding: 6px 14px;
    font-size: 14px;
    cursor: pointer;
    border-radius: 20px;
    border: none;
    background-color: var(--btn-bg);
    color: white;
    transition: 0.3s;
}

#darkModeToggle:hover {
    background-color: var(--btn-hover);
    transform: scale(1.05);
}

/* ===============================
   HERO SECTION
================================ */
.hero {
    text-align: center;
    padding: 100px 20px;
    background: var(--bg-hero);
    color: white;
}

.hero h1 {
    font-size: 42px;
    margin-bottom: 20px;
}

.hero p {
    max-width: 700px;
    margin: 0 auto 30px auto;
    font-size: 18px;
}

.btn {
    padding: 14px 30px;
    background-color: var(--btn-bg);
    color: white;
    font-weight: bold;
    border-radius: 6px;
    text-decoration: none;
    transition: 0.3s;
}

.btn:hover {
    background-color: var(--btn-hover);
    transform: translateY(-2px);
}

/* ===============================
   SECTION UMUM
================================ */
.about {
    max-width: 1000px;
    margin: 60px auto;
    padding: 0 40px;
}

.about h2,
.about h3 {
    color: var(--text-dark);
}

.about h2 {
    margin-bottom: 20px;
    text-align: center;
}

.about h3 {
    margin-top: 30px;
    margin-bottom: 10px;
}

.about p {
    margin-bottom: 15px;
}

.about ul {
    max-width: 900px;
    margin: 20px auto;
    padding-left: 20px;
}

.about ul li {
    margin-bottom: 10px;
}

.about-center {
    text-align: center;
}

.about-center p {
    text-align: center;
}

/* ===============================
   TOPIC CARDS
================================ */
.topics {
    display: flex;
    justify-content: center;
    gap: 30px;
    padding: 40px;
    flex-wrap: wrap;
}

.card,
.youtube-card {
    background-color: var(--bg-card);
    padding: 25px;
    width: 260px;
    border-radius: 10px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    text-align: center;
    transition: 0.3s;
    color: var(--text-main);
}

.card:hover,
.youtube-card:hover {
    transform: translateY(-5px);
}

.card h3 {
    margin-bottom: 15px;
}

.more-btn {
    display: inline-block;
    margin-top: 15px;
    padding: 8px 15px;
    background-color: var(--btn-bg);
    color: white;
    text-decoration: none;
    border-radius: 5px;
    font-size: 14px;
    transition: 0.3s;
}

.more-btn:hover {
    background-color: var(--btn-hover);
}

/* ===============================
   YOUTUBE SECTION
================================ */
.youtube-section {
    display: flex;
    justify-content: center;
    gap: 30px;
    flex-wrap: wrap; /* supaya responsif di layar kecil */
    padding: 20px 0;
}

/* ===============================
   YOUTUBE CARD IMAGE
================================ */
.youtube-card img {
    width: 110px;
    height: 110px;
    border-radius: 50%;
    object-fit: cover;
    margin-bottom: 15px;
}

/* ===============================
   VIDEO
================================ */
iframe {
    width: 100%;
    max-width: 700px;
    height: 380px;
    border: none;
    border-radius: 10px;
    display: block;
    margin: 20px auto;
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}

/* ===============================
   FOOTER
================================ */
footer {
    text-align: center;
    padding: 25px;
    background-color: var(--bg-footer);
    color: white;
    margin-top: 60px;
}

/* ===============================
   RESPONSIVE
================================ */
@media (max-width: 900px) {
    .topics,
    .youtube-section {
        justify-content: center;
        gap: 20px;
    }

    nav {
        padding: 18px 5%;
    }

    .hero h1 {
        font-size: 34px;
    }

    .hero p {
        font-size: 16px;
    }
}

@media (max-width: 600px) {
    .nav-links a {
        margin-left: 15px;
        font-size: 14px;
    }

    .btn {
        padding: 12px 24px;
        font-size: 14px;
    }

    .card,
    .youtube-card {
        width: 90%; /* card mengikuti lebar layar di HP */
    }

    .hero h1 {
        font-size: 28px;
    }

    .hero p {
        font-size: 14px;
    }
}

/* ===============================
   MODAL LIGHT MODE WARNING
================================ */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.7);
    display: flex;
    justify-content: center;
    align-items: center;
    opacity: 0;
    pointer-events: none;
    transition: opacity 0.3s ease;
    z-index: 3000;
}

.modal.show {
    opacity: 1;
    pointer-events: auto;
}

.modal-content {
    background-color: var(--bg-card);
    color: var(--text-dark);
    padding: 40px 30px;
    border-radius: 15px;
    text-align: center;
    max-width: 400px;
    width: 90%;
    box-shadow: 0 8px 20px rgba(0,0,0,0.3);
}

.modal-content h2 {
    margin-bottom: 20px;
    font-size: 28px;
}

.modal-content p {
    margin-bottom: 25px;
    font-size: 18px;
}

.modal-buttons button {
    padding: 10px 20px;
    margin: 0 10px;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    font-weight: bold;
    transition: 0.3s;
}

#confirmLight {
    background-color: #facc15; /* kuning sebagai warning */
    color: #1e293b;
}

#confirmLight:hover {
    background-color: #eab308;
}

#cancelLight {
    background-color: #f87171; /* merah untuk batal */
    color: white;
}

#cancelLight:hover {
    background-color: #ef4444;
}