/* ==========================================================================
   TUBER Premium Design System (Light Mode: Clean White & Deep Navy)
   Based on Impeccable Design Standards
   ========================================================================== */

:root {
    /* Base Surfaces */
    --tuber-bg: #FFFFFF;
    --tuber-bg-sub: #F8FAFC;
    --tuber-bg-card: #FFFFFF;
    --tuber-bg-card-hover: #F8FAFC;
    
    /* Brand & Deep Navy Palette (Extreme Clarity) */
    --tuber-navy-950: #0B132B;
    --tuber-navy-900: #0F172A; /* Main Headline: Ultra Sharp Contrast */
    --tuber-navy-800: #1E293B; /* Subtitles & Titles */
    --tuber-navy-700: #334155; /* Secondary text */
    --tuber-navy-600: #475569; /* Body copy */
    --tuber-navy-400: #94A3B8; /* Muted hints */
    
    /* Primary & Vibrant Accents */
    --tuber-primary: #1D4ED8;     /* Royal Navy Blue */
    --tuber-primary-hover: #1E40AF;
    --tuber-primary-light: #EFF6FF;
    --tuber-accent-cyan: #0284C7;
    --tuber-accent-violet: #6366F1;
    --tuber-accent-pink: #EC4899;
    
    /* Borders & Dividers */
    --tuber-border: #E2E8F0;
    --tuber-border-light: #F1F5F9;
    --tuber-border-card: rgba(15, 23, 42, 0.08);
    
    /* Elevation Shadows (Soft Clay & Modern SaaS Depth) */
    --tuber-shadow-sm: 0 2px 8px rgba(15, 23, 42, 0.04);
    --tuber-shadow-md: 0 10px 30px -4px rgba(15, 23, 42, 0.08), 0 4px 6px -2px rgba(15, 23, 42, 0.03);
    --tuber-shadow-lg: 0 20px 45px -8px rgba(15, 23, 42, 0.12);
    --tuber-shadow-hover: 0 25px 50px -10px rgba(29, 78, 216, 0.15);
    
    /* Glassmorphism Light */
    --tuber-glass: rgba(255, 255, 255, 0.9);
    --tuber-glass-border: rgba(226, 232, 240, 0.9);
}

body {
    background-color: var(--tuber-bg) !important;
    color: var(--tuber-navy-900);
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif !important;
    -webkit-font-smoothing: antialiased;
}

/* Premium Card Components */
.tuber-glass-card {
    background: #FFFFFF;
    border: 1px solid var(--tuber-border);
    border-radius: 28px;
    box-shadow: var(--tuber-shadow-md);
    transition: all 0.35s cubic-bezier(0.16, 1, 0.3, 1);
}

.tuber-glass-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--tuber-shadow-hover);
    border-color: #BFDBFE;
}

/* Header Light Mode */
#header {
    background: rgba(255, 255, 255, 0.88) !important;
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    border-bottom: 1px solid var(--tuber-border) !important;
    box-shadow: 0 4px 20px rgba(15, 23, 42, 0.03) !important;
}

#header .gnb > li > a {
    color: var(--tuber-navy-900) !important;
    font-weight: 700;
    font-size: 15px;
    letter-spacing: -0.02em;
    transition: color 0.2s ease;
}

#header .gnb > li > a:hover {
    color: var(--tuber-primary) !important;
}

/* Button Refinement */
.btn-premium {
    padding: 14px 34px;
    border-radius: 16px;
    font-weight: 700;
    font-size: 16px;
    transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    cursor: pointer;
}

.btn-premium-primary {
    background: var(--tuber-navy-900);
    color: #FFFFFF !important;
    box-shadow: 0 10px 25px rgba(15, 23, 42, 0.2);
}

.btn-premium-primary:hover {
    background: var(--tuber-primary);
    transform: translateY(-3px);
    box-shadow: 0 15px 35px rgba(29, 78, 216, 0.3);
}

.btn-premium-secondary {
    background: #FFFFFF;
    color: var(--tuber-navy-900) !important;
    border: 1px solid var(--tuber-border);
    box-shadow: var(--tuber-shadow-sm);
}

.btn-premium-secondary:hover {
    background: var(--tuber-bg-sub);
    border-color: #CBD5E1;
    transform: translateY(-2px);
}