/* --- CSS Variables --- */
:root {
    --tg-primary: #2AABEE;
    --tg-primary-hover: #228cc2;
    --bg-dark: #0f172a;
    --bg-card: #1e293b;
    --text-main: #f8fafc;
    --text-muted: #94a3b8;
    --transition-speed: 0.3s;
}

/* --- Global Styles --- */
body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-dark);
    color: var(--text-main);
    overflow-x: hidden;
}

html {
    scroll-behavior: smooth;
}

/* --- Typography & Utilities --- */
.text-primary {
    color: var(--tg-primary) !important;
}

.bg-primary {
    background-color: var(--tg-primary) !important;
}

.btn-primary {
    background-color: var(--tg-primary);
    border-color: var(--tg-primary);
    transition: all var(--transition-speed);
}

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

.text-gradient {
    background: linear-gradient(90deg, #2AABEE, #0088cc);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.bg-light-dark {
    background-color: #0b1120;
}

/* --- Navbar --- */
#mainNav {
    transition: all 0.4s ease;
    padding: 1.5rem 0;
}

#mainNav.scrolled {
    background-color: rgba(15, 23, 42, 0.95);
    backdrop-filter: blur(10px);
    padding: 1rem 0;
    box-shadow: 0 4px 20px rgba(0,0,0,0.3);
}

.navbar-dark .navbar-nav .nav-link {
    color: var(--text-main);
    font-weight: 600;
    margin: 0 0.5rem;
    transition: color var(--transition-speed);
}

.navbar-nav .nav-link:hover {
    color: var(--tg-primary);
}

/* --- Hero Section --- */
.hero-section {
    min-height: 100vh;
    background: radial-gradient(circle at center, #1e293b 0%, #0f172a 100%);
    position: relative;
    padding-top: 80px;
}

/* --- Features Section --- */
.feature-card {
    background-color: var(--bg-card);
    border: 1px solid rgba(255, 255, 255, 0.05);
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: 0 20px 40px rgba(0,0,0,0.4) !important;
}

.bg-primary-soft {
    background-color: rgba(42, 171, 238, 0.1);
    width: 80px;
    height: 80px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* --- Article Section --- */
.article-content p {
    line-height: 1.8;
}

.article-content strong {
    color: var(--text-main);
}

/* --- Back to Top Button --- */
#backToTop {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-speed);
    z-index: 1000;
}

#backToTop.visible {
    opacity: 1;
    visibility: visible;
}

/* --- Animations (Intersection Observer) --- */
.animate-on-scroll {
    opacity: 0;
    transform: translateY(40px);
    transition: opacity 0.8s ease-out, transform 0.8s ease-out;
}

.animate-on-scroll.is-visible {
    opacity: 1;
    transform: translateY(0);
}