:root {
    --primary-blue: #008cff;
    --primary-blue-dark: #003d6e;
    --primary-blue-light: #92ceff;
    --bg-light: #f8fafc;
    --bg-dark: #0f172a;
    --text-light: #1e293b;
    --text-dark: #e2e8f0;
    --card-bg-light: rgba(255, 255, 255, 0.8);
    --card-bg-dark: rgba(15, 23, 42, 0.8);
    --glass-border-light: rgba(255, 255, 255, 0.2);
    --glass-border-dark: rgba(255, 255, 255, 0.1);
    --shadow-light: 0 8px 32px rgba(0, 0, 0, 0.1);
    --shadow-dark: 0 8px 32px rgba(0, 0, 0, 0.3);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    line-height: 1.6;
    transition: background-color 0.3s ease, color 0.3s ease;
    overflow-x: hidden;
}

body.light-theme {
    background: linear-gradient(135deg, var(--bg-light) 0%, #e0f2fe 100%);
    color: var(--text-light);
}

body.dark-theme {
    background: linear-gradient(135deg, var(--bg-dark) 0%, #1e293b 100%);
    color: var(--text-dark);
}

/* Loading Screen */
.loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-blue-dark) 100%);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;
    transition: opacity 0.5s ease, visibility 0.5s ease;
}

.loading-screen.hidden {
    opacity: 0;
    visibility: hidden;
}

.loading-content {
    text-align: center;
}

.loading-spinner {
    width: 50px;
    height: 50px;
    border: 3px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.loading-text {
    color: white;
    font-size: 1.2rem;
    font-weight: 500;
}

/* Header */
.header {
    padding: 1rem 0;
    background: rgba(255, 255, 255, 0.1);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--glass-border-light);
    position: sticky;
    top: 0;
    z-index: 100;
    transition: all 0.3s ease;
}

body.dark-theme .header {
    background: rgba(15, 23, 42, 0.5);
    border-bottom: 1px solid var(--glass-border-dark);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 1rem;
}

.header .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.8rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-blue-dark) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Theme Toggle */
.theme-toggle {
    background: none;
    border: 2px solid currentColor;
    border-radius: 50%;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.3s ease;
    color: inherit;
}

.theme-toggle:hover {
    transform: scale(1.1);
    border-color: var(--primary-blue);
}

.theme-toggle svg {
    width: 24px;
    height: 24px;
    transition: transform 0.3s ease;
}

body.light-theme .sun-icon {
    display: none;
}

body.dark-theme .moon-icon {
    display: none;
}

/* Language Selector */
.lang-selector {
    display: flex;
    gap: 0.5rem;
    margin-right: 1rem;
}

.lang-btn {
    background: rgba(255, 255, 255, 0.1);
    border: 2px solid rgba(255, 255, 255, 0.3);
    color: inherit;
    padding: 0.5rem 0.8rem;
    border-radius: 8px;
    cursor: pointer;
    font-weight: 600;
    font-size: 0.9rem;
    transition: all 0.3s ease;
}

.lang-btn:hover {
    background: rgba(255, 255, 255, 0.2);
    transform: translateY(-2px);
}

.lang-btn.active {
    background: var(--primary-blue);
    border-color: var(--primary-blue);
    color: white;
}

body.dark-theme .lang-btn {
    background: rgba(15, 23, 42, 0.7);
    border-color: rgba(255, 255, 255, 0.2);
}

body.dark-theme .lang-btn.active {
    background: var(--primary-blue);
    color: white;
}

/* Hero Section */
.hero {
    min-height: calc(100vh - 80px);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 2rem 0;
}

.hero-content {
    text-align: center;
    max-width: 600px;
}

.hero-title {
    font-size: clamp(2.5rem, 8vw, 4rem);
    font-weight: 700;
    margin-bottom: 1rem;
    animation: fadeInUp 0.8s ease;
}

.hero-subtitle {
    font-size: clamp(1.1rem, 3vw, 1.5rem);
    opacity: 0.8;
    margin-bottom: 3rem;
    animation: fadeInUp 0.8s ease 0.2s both;
}

/* DateTime Display */
.datetime-container {
    background: var(--card-bg-light);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border-light);
    border-radius: 20px;
    padding: 2rem;
    box-shadow: var(--shadow-light);
    animation: fadeInUp 0.8s ease 0.4s both;
    transition: all 0.3s ease;
}

body.dark-theme .datetime-container {
    background: var(--card-bg-dark);
    border: 1px solid var(--glass-border-dark);
    box-shadow: var(--shadow-dark);
}

.time-display {
    font-size: clamp(2.5rem, 8vw, 4rem);
    font-weight: 700;
    font-variant-numeric: tabular-nums;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--primary-blue-dark) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.date-display {
    font-size: clamp(1rem, 3vw, 1.2rem);
    opacity: 0.8;
}

/* Features Section */
.features {
    padding: 4rem 0;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 3rem;
}

.feature-card {
    background: var(--card-bg-light);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border-light);
    border-radius: 20px;
    padding: 2rem;
    text-align: center;
    transition: all 0.3s ease;
    animation: fadeInUp 0.8s ease;
}

body.dark-theme .feature-card {
    background: var(--card-bg-dark);
    border: 1px solid var(--glass-border-dark);
}

.feature-card:hover {
    transform: translateY(-10px);
    box-shadow: var(--shadow-light);
}

body.dark-theme .feature-card:hover {
    box-shadow: var(--shadow-dark);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.feature-card h3 {
    font-size: 1.3rem;
    margin-bottom: 0.5rem;
    color: var(--primary-blue-dark);
}

.feature-card p {
    opacity: 0.8;
}

/* Animations */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Responsive */
@media (max-width: 768px) {
    .header .container {
        padding: 0 1rem;
    }
    
    .datetime-container {
        padding: 1.5rem;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
        gap: 1.5rem;
    }
    
    .lang-selector {
        gap: 0.3rem;
        margin-right: 0.5rem;
    }
    
    .lang-btn {
        padding: 0.4rem 0.6rem;
        font-size: 0.8rem;
    }
}