/* =====================================
   Engineering Calculator Website
   10/10 Professional Stylesheet
===================================== */

/* ---------- CSS Variables & Theming ---------- */
:root {
    --bg-color: #f7f9fc;
    --text-main: #111827;
    --text-muted: #4b5563;
    --card-bg: #ffffff;
    --header-bg: rgba(255, 255, 255, 0.95);
    --border-color: #e5e7eb;
    --primary: #1565c0;
    --primary-hover: #0d47a1;
    --accent: #ff9800;
    --accent-hover: #f57c00;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.08);
}

/* Dark Mode Variables */
[data-theme="dark"] {
    --bg-color: #111827;
    --text-main: #f9fafb;
    --text-muted: #9ca3af;
    --card-bg: #1f2937;
    --header-bg: rgba(31, 41, 55, 0.95);
    --border-color: #374151;
    --primary: #60a5fa;
    --primary-hover: #93c5fd;
    --shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

/* ---------- Global Reset & Typography ---------- */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: "Inter", system-ui, sans-serif;
    background: var(--bg-color);
    color: var(--text-main);
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: auto;
}

/* ---------- Header & Navigation ---------- */
.header {
    background: var(--header-bg);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 1000;
    backdrop-filter: blur(10px); /* Modern blur effect */
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 75px;
}

.logo {
    font-size: 24px;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
}

nav {
    display: flex;
    gap: 30px;
}

nav a {
    text-decoration: none;
    color: var(--text-muted);
    font-weight: 500;
    transition: color 0.2s ease;
}

nav a:hover {
    color: var(--primary);
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 15px;
}

#theme-toggle {
    background: none;
    border: none;
    font-size: 20px;
    cursor: pointer;
    color: var(--text-main);
    transition: transform 0.2s;
}

#theme-toggle:hover {
    transform: scale(1.1);
}

.menu-btn {
    display: none;
    font-size: 25px;
    border: none;
    background: none;
    color: var(--text-main);
    cursor: pointer;
}

/* ---------- Hero Section ---------- */
.hero {
    background: linear-gradient(135deg, #1565c0, #0d47a1);
    color: white;
    padding: 100px 0;
    text-align: center;
}

.hero h1 {
    font-size: clamp(32px, 5vw, 48px); /* Fluid typography */
    line-height: 1.2;
    margin-bottom: 20px;
}

.hero p {
    font-size: clamp(16px, 2vw, 20px);
    max-width: 750px;
    margin: 0 auto 40px;
    opacity: 0.95;
}

/* Search Bar */
.search {
    display: flex;
    justify-content: center;
    max-width: 650px;
    margin: auto;
    box-shadow: 0 4px 20px rgba(0,0,0,0.15);
    border-radius: 8px;
}

.search input {
    flex: 1;
    padding: 16px 20px;
    border: none;
    border-radius: 8px 0 0 8px;
    font-size: 16px;
    outline: none;
    background: #ffffff;
    color: #111827;
}

.search button {
    padding: 16px 30px;
    border: none;
    background: var(--accent);
    color: white;
    font-weight: bold;
    cursor: pointer;
    border-radius: 0 8px 8px 0;
    transition: background 0.2s;
}

.search button:hover {
    background: var(--accent-hover);
}

/* ---------- Sections & Grids ---------- */
section {
    padding: 70px 0;
}

.section-title {
    text-align: center;
    font-size: 36px;
    margin-bottom: 40px;
    color: var(--text-main);
}

.cards {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 30px;
}

.card {
    background: var(--card-bg);
    padding: 35px 25px;
    border-radius: 15px;
    text-align: center;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    text-decoration: none;
    display: block;
}

.card:hover {
    transform: translateY(-8px);
    box-shadow: 0 15px 35px rgba(0, 0, 0, 0.1);
}

.card .icon {
    font-size: 40px;
    display: block;
    margin-bottom: 10px;
}

.card h3 {
    margin: 15px 0 10px;
    font-size: 22px;
    color: var(--primary);
}

.card p {
    color: var(--text-muted);
    font-size: 15px;
}

.hidden {
    display: none !important;
}

#no-results {
    text-align: center;
    padding: 40px;
    color: var(--text-muted);
}

/* ---------- AdSense Anti-CLS Containers ---------- */
.ad-container {
    background: var(--border-color);
    margin: 40px auto;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 8px;
    color: var(--text-muted);
    font-size: 12px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* Pre-reserve space to prevent layout shifting when ads load */
.ad-leaderboard {
    min-height: 90px;
    max-width: 728px;
}

/* ---------- Footer ---------- */
footer {
    background: #0d47a1;
    color: white;
    padding: 40px 0;
    text-align: center;
    margin-top: 50px;
}

.footer-links {
    margin-top: 15px;
}

.footer-links a {
    color: #93c5fd;
    text-decoration: none;
    margin: 0 10px;
    font-size: 14px;
}

.footer-links a:hover {
    text-decoration: underline;
}

/* ---------- Animations ---------- */
.animate-fade-up {
    animation: fadeUp 0.8s ease forwards;
    opacity: 0;
    transform: translateY(20px);
}

@keyframes fadeUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.fade-in-scroll {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in-scroll.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ---------- Mobile Responsive ---------- */
@media (max-width: 768px) {
    nav {
        position: absolute;
        top: 75px;
        left: 0;
        width: 100%;
        background: var(--card-bg);
        flex-direction: column;
        gap: 0;
        border-bottom: 1px solid var(--border-color);
        box-shadow: 0 10px 15px -3px rgba(0,0,0,0.1);
        
        /* Mobile Menu Animation setup */
        max-height: 0;
        overflow: hidden;
        transition: max-height 0.4s ease;
    }

    nav.nav-open {
        max-height: 300px; /* Expands menu */
    }

    nav a {
        padding: 15px 20px;
        border-bottom: 1px solid var(--border-color);
        display: block;
        color: var(--text-main);
    }

    .menu-btn {
        display: block;
    }

    .search {
        flex-direction: column;
    }

    .search input {
        border-radius: 8px;
        margin-bottom: 10px;
    }

    .search button {
        border-radius: 8px;
        width: 100%;
    }
}