:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --accent: #059669;
    --bg-main: #f8fafc;
    --bg-card: #ffffff;
    --text-title: #0f172a;
    --text-body: #334155;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
    --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1);
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Plus Jakarta Sans', sans-serif;
}

body.theme-modern {
    background-color: var(--bg-main);
    color: var(--text-body);
    min-height: 100vh;
}

/* Header Navbar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2rem;
    background: var(--bg-card);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 800;
    font-size: 1.25rem;
    color: var(--primary);
}

.nav-btn {
    background: transparent;
    border: none;
    padding: 0.5rem 1rem;
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-body);
    cursor: pointer;
    border-radius: 6px;
    transition: all 0.2s;
}

.nav-btn.active, .nav-btn:hover {
    color: var(--primary);
    background: #eff6ff;
}

/* Page Layout */
.page-section {
    display: none;
    max-width: 1100px;
    margin: 2rem auto;
    padding: 0 1.5rem;
}

.page-section.active {
    display: block;
    animation: fadeIn 0.3s ease-out;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Hero Section */
.hero-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 2rem;
    align-items: center;
}

.badge {
    background: #dbeafe;
    color: var(--primary);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.85rem;
    font-weight: 700;
}

.hero-title {
    font-size: 2.5rem;
    color: var(--text-title);
    line-height: 1.2;
    margin: 1rem 0;
}

.hero-title .highlight {
    color: var(--primary);
}

.hero-cards-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.feature-card {
    background: var(--bg-card);
    padding: 1.25rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
}

/* Materi Layout */
.materi-container {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 1.5rem;
}

.materi-sidebar {
    background: var(--bg-card);
    padding: 1.25rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

.materi-sidebar ul {
    list-style: none;
    margin-top: 1rem;
}

.materi-sidebar li {
    padding: 0.75rem 1rem;
    border-radius: 8px;
    margin-bottom: 0.5rem;
    cursor: pointer;
    font-weight: 600;
}

.materi-sidebar li.active {
    background: var(--primary);
    color: #ffffff;
}

.materi-body-card {
    background: var(--bg-card);
    padding: 2rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    line-height: 1.7;
}

/* Simulator Grid */
.simulator-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    margin-top: 1.5rem;
}

.sim-inputs-card, .sim-outputs-card {
    background: var(--bg-card);
    padding: 1.5rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
}

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

.form-group label {
    display: block;
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: 0.4rem;
}

.form-group input, .input-select, textarea {
    width: 100%;
    padding: 0.65rem;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 0.95rem;
}

.highlight-box {
    background: #ecfdf5;
    border: 1px solid #10b981;
    padding: 1rem;
    border-radius: 8px;
    margin-top: 1rem;
}

/* Buttons */
.btn-primary, .btn-cta, .btn-accent, .btn-secondary {
    padding: 0.75rem 1.25rem;
    border: none;
    border-radius: 8px;
    font-weight: 700;
    cursor: pointer;
    transition: background 0.2s;
}

.btn-primary, .btn-cta { background: var(--primary); color: #fff; }
.btn-accent { background: var(--accent); color: #fff; }
.btn-secondary { background: #e2e8f0; color: var(--text-title); }

/* Modals & Tables */
.modal-overlay {
    display: none;
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.5);
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal-card {
    background: var(--bg-card);
    padding: 2rem;
    border-radius: 12px;
    width: 90%;
    max-width: 400px;
    position: relative;
}

.login-form { display: none; }
.login-form.active { display: block; }

.data-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1rem;
    background: var(--bg-card);
}

.data-table th, .data-table td {
    border: 1px solid var(--border-color);
    padding: 0.75rem 1rem;
    text-align: left;
}

.hidden { display: none; }