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

:root {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #64748b;
    --secondary-hover: #475569;
    --background: #f8fafc;
    --surface: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --error: #ef4444;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen',
        'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue',
        sans-serif;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    background: var(--background);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

.container {
    max-width: 500px;
    width: 100%;
}

.header {
    text-align: center;
    margin-bottom: 48px;
}

.header h1 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 12px;
    color: var(--text-primary);
}

.header p {
    font-size: 16px;
    color: var(--text-secondary);
}

.button-container {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 20px 32px;
    border: none;
    border-radius: 12px;
    font-size: 18px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    box-shadow: var(--shadow);
    background: var(--surface);
}

.btn:active {
    transform: scale(0.98);
}

.btn svg {
    width: 24px;
    height: 24px;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--primary-hover);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: var(--surface);
    color: var(--text-primary);
    border: 2px solid var(--secondary-color);
}

.btn-secondary:hover {
    background: var(--background);
    border-color: var(--secondary-hover);
}

.loading-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.7);
    z-index: 1000;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 20px;
}

.loading-overlay.active {
    display: flex;
}

.loading-overlay p {
    color: white;
    font-size: 18px;
    font-weight: 500;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 4px solid rgba(255, 255, 255, 0.3);
    border-top-color: white;
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}

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

.error-message {
    display: none;
    margin-top: 20px;
    padding: 16px;
    background: #fee2e2;
    color: var(--error);
    border-radius: 8px;
    font-size: 14px;
    text-align: center;
}

.error-message.active {
    display: block;
}

/* Mobile optimizations */
@media (max-width: 480px) {
    .header h1 {
        font-size: 28px;
    }

    .header p {
        font-size: 14px;
    }

    .btn {
        padding: 18px 24px;
        font-size: 16px;
    }
}

/* Touch device optimizations */
@media (hover: none) {
    .btn:hover {
        transform: none;
    }

    .btn:active {
        transform: scale(0.95);
    }
}