/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Color Palette */
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --secondary-color: #64748b;
    --success-color: #059669;
    --warning-color: #d97706;
    --error-color: #dc2626;
    
    /* Neutral Colors */
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;
    --border-focus: #3b82f6;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Typography */
    --font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;
    --font-size-3xl: 1.875rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    
    /* Border Radius */
    --radius-sm: 0.25rem;
    --radius-md: 0.5rem;
    --radius-lg: 0.75rem;
    --radius-xl: 1rem;
    
    /* Transitions */
    --transition-fast: 150ms ease-in-out;
    --transition-normal: 250ms ease-in-out;
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-primary: #0f172a;
        --bg-secondary: #1e293b;
        --bg-tertiary: #334155;
        --text-primary: #f8fafc;
        --text-secondary: #cbd5e1;
        --text-muted: #64748b;
        --border-color: #334155;
    }
}

body {
    font-family: var(--font-family);
    font-size: var(--font-size-base);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    overflow-x: hidden;
}

/* Application Layout */
#app {
    display: grid;
    grid-template-rows: auto 1fr auto;
    min-height: 100vh;
    background-color: var(--bg-primary);
}

/* Header Styles */
.app-header {
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md) var(--spacing-lg);
}

.app-title {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--primary-color);
    margin: 0;
}

.header-nav {
    display: flex;
    gap: var(--spacing-sm);
}

/* Button Styles */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: var(--font-size-base);
    font-weight: 500;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    text-decoration: none;
    background: none;
    min-height: 2.5rem;
}

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

.btn-primary:hover:not(:disabled) {
    background-color: var(--primary-hover);
    border-color: var(--primary-hover);
}

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

.btn-secondary:hover:not(:disabled) {
    background-color: var(--bg-tertiary);
    color: var(--text-primary);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.nav-btn {
    padding: var(--spacing-sm);
    border-radius: var(--radius-md);
    background: none;
    border: 1px solid transparent;
    cursor: pointer;
    font-size: var(--font-size-lg);
    transition: all var(--transition-fast);
}

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

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

/* Main Content */
.main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-lg);
    width: 100%;
}

/* Screen Management */
.screen {
    display: none;
    animation: fadeIn var(--transition-normal);
}

.screen.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

.screen-content {
    margin: 0 auto;
}

.screen h2 {
    font-size: var(--font-size-2xl);
    font-weight: 700;
    margin-bottom: var(--spacing-xl);
    color: var(--text-primary);
}

/* Utility Classes */
.hidden {
    display: none !important;
}

.loading-indicator {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-2xl);
    color: var(--text-secondary);
}

.spinner {
    width: 2rem;
    height: 2rem;
    border: 2px solid var(--border-color);
    border-top: 2px solid var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin-bottom: var(--spacing-md);
}

.spinner.large {
    width: 3rem;
    height: 3rem;
    border-width: 3px;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Status Bar */
.status-bar {
    background-color: var(--bg-secondary);
    border-top: 1px solid var(--border-color);
    padding: var(--spacing-sm) var(--spacing-lg);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
}

.status-message {
    flex: 1;
    transition: color var(--transition-fast);
}

.status-message.success {
    color: var(--success-color);
}

.status-message.error {
    color: var(--error-color);
}

.status-message.warning {
    color: var(--warning-color);
}

.status-message.info {
    color: var(--primary-color);
}

.progress-container {
    display: flex;
    align-items: center;
    gap: var(--spacing-md);
    flex: 0 0 200px;
}

.progress-bar {
    flex: 1;
    height: 0.5rem;
    background-color: var(--bg-tertiary);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background-color: var(--primary-color);
    transition: width var(--transition-normal);
    width: 0%;
}

.progress-text {
    flex: 0 0 auto;
    font-weight: 500;
}

/* Loading Screen */
.loading-screen {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background-color: var(--bg-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;
}

.loading-content {
    text-align: center;
    color: var(--text-secondary);
}

/* Responsive Design */
@media (max-width: 768px) {
    .header-content {
        padding: var(--spacing-sm) var(--spacing-md);
    }
    
    .app-title {
        font-size: var(--font-size-lg);
    }
    
    .main-content {
        padding: var(--spacing-md);
    }
    
    .screen h2 {
        font-size: var(--font-size-xl);
        margin-bottom: var(--spacing-lg);
    }
}

@media (max-width: 480px) {
    .header-content {
        padding: var(--spacing-sm);
    }
    
    .btn {
        padding: var(--spacing-xs) var(--spacing-sm);
        font-size: var(--font-size-sm);
    }
    
    .nav-btn {
        padding: var(--spacing-xs);
        font-size: var(--font-size-base);
    }
}