/* Modern Header & Navigation */
.site-header {
    background: var(--card);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}
.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0.75rem 1rem;
    max-width: 1400px;
}
.brand {
    font-weight: 700;
    font-size: 1.25rem;
    color: var(--primary);
    text-decoration: none;
    white-space: nowrap;
}
.main-nav {
    display: flex;
    align-items: center;
    gap: 0.25rem;
    flex-wrap: wrap;
}
.nav-link {
    padding: 0.5rem 0.75rem;
    color: var(--text);
    text-decoration: none;
    border-radius: 6px;
    font-size: 0.9rem;
    white-space: nowrap;
    transition: background 0.15s;
}
.nav-link:hover, .nav-link.active {
    background: var(--primary);
    color: white;
}
.nav-dropdown { position: relative; }
.dropdown-menu {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    background: white;
    border: 1px solid var(--border);
    border-radius: 8px;
    min-width: 220px;
    box-shadow: 0 8px 24px rgba(0,0,0,0.12);
    z-index: 200;
    padding: 0.5rem 0;
}
.nav-dropdown:hover .dropdown-menu,
.nav-dropdown:focus-within .dropdown-menu {
    display: block;
}
.dropdown-item {
    display: block;
    padding: 0.5rem 1rem;
    color: var(--text);
    text-decoration: none;
    font-size: 0.9rem;
}
.dropdown-item:hover { background: #f3f4f6; }

/* Hamburger */
.nav-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}
.nav-toggle span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--text);
    margin: 5px 0;
    transition: 0.2s;
}

@media (max-width: 1024px) {
    .nav-toggle { display: block; }
    .main-nav {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--card);
        flex-direction: column;
        align-items: stretch;
        padding: 1rem;
        border-bottom: 1px solid var(--border);
        box-shadow: 0 8px 16px rgba(0,0,0,0.1);
    }
    .main-nav.open { display: flex; }
    .nav-link { padding: 0.75rem 1rem; }
    .dropdown-menu {
        position: static;
        box-shadow: none;
        border: none;
        background: transparent;
        display: block;
        padding-left: 1rem;
    }
}

/* Existing styles continue below */
:root {
    --primary: #2563eb;
    --bg: #ffffff;
    --text: #1f2937;
    --card: #f9fafb;
    --border: #e5e7eb;
}
[data-theme="dark"] {
    --bg: #111827;
    --text: #f9fafb;
    --card: #1f2937;
    --border: #374151;
}
* { box-sizing: border-box; }
body { font-family: system-ui, -apple-system, sans-serif; margin: 0; background: var(--bg); color: var(--text); line-height: 1.6; }
.container { max-width: 1200px; margin: 0 auto; padding: 1rem; }
header { background: var(--card); border-bottom: 1px solid var(--border); padding: 1rem 0; }
header .container { display: flex; justify-content: space-between; align-items: center; }
nav a { margin-left: 1.5rem; color: var(--text); text-decoration: none; }
.hero { text-align: center; padding: 3rem 1rem; }
.tools-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.5rem; margin: 2rem 0; }
.tool-card { background: var(--card); border: 1px solid var(--border); border-radius: 8px; padding: 1.5rem; transition: transform 0.2s; }
.tool-card:hover { transform: translateY(-4px); }
.tool-card h3 { margin: 0 0 0.5rem; }
.btn { display: inline-block; padding: 0.5rem 1rem; background: var(--primary); color: white; text-decoration: none; border-radius: 4px; border: none; cursor: pointer; }
.btn:hover { opacity: 0.9; }
footer { border-top: 1px solid var(--border); padding: 2rem 0; margin-top: 3rem; text-align: center; color: #6b7280; }
.login-page { display: flex; align-items: center; justify-content: center; min-height: 100vh; background: #f3f4f6; }
.login-box { background: white; padding: 2rem; border-radius: 8px; box-shadow: 0 4px 6px rgba(0,0,0,0.1); width: 100%; max-width: 400px; }
.form-group { margin-bottom: 1rem; }
.form-group label { display: block; margin-bottom: 0.25rem; font-weight: 500; }
.form-group input { width: 100%; padding: 0.5rem; border: 1px solid #d1d5db; border-radius: 4px; }
.alert.error { background: #fee2e2; color: #991b1b; padding: 0.75rem; border-radius: 4px; margin-bottom: 1rem; }
/* Converter */
.converter { max-width: 600px; margin: 2rem auto; }
.dropzone { border: 2px dashed #d1d5db; padding: 2rem; text-align: center; border-radius: 8px; cursor: pointer; }
.preview img { max-width: 100%; margin-top: 1rem; }