/* CSS Reset */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* CSS Custom Properties */
:root {
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-secondary: #64748b;
    --color-accent: #0ea5e9;
    --color-neutral-100: #f8fafc;
    --color-neutral-200: #e2e8f0;
    --color-neutral-300: #cbd5e1;
    --color-neutral-400: #94a3b8;
    --color-neutral-500: #64748b;
    --color-neutral-600: #475569;
    --color-neutral-700: #334155;
    --color-neutral-800: #1e293b;
    --color-neutral-900: #0f172a;
    
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
    
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    
    --border-radius-sm: 0.25rem;
    --border-radius-md: 0.375rem;
    --border-radius-lg: 0.5rem;
    
    --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);
}

/* Base Styles */
html {
    font-size: 16px;
    line-height: 1.5;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-sans);
    color: var(--color-neutral-800);
    background-color: var(--color-neutral-100);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.25;
    margin-bottom: var(--spacing-md);
}

h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }

/* Layout */
.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

.section {
    padding: var(--spacing-xl) 0;
}

/* Header & Navigation */
.main-header {
    background-color: white;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-primary);
}

.nav-links {
    display: flex;
    gap: var(--spacing-md);
}

.nav-link {
    color: var(--color-neutral-600);
    text-decoration: none;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    transition: all 0.2s ease;
}

.nav-link:hover {
    color: var(--color-primary);
    background-color: var(--color-neutral-100);
}

/* Buttons */
.btn-primary, .btn-secondary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-sm) var(--spacing-lg);
    border-radius: var(--border-radius-md);
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
    border: none;
    min-height: 44px; /* Mobile touch target */
}

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

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

.btn-secondary {
    background-color: var(--color-neutral-200);
    color: var(--color-neutral-700);
}

.btn-secondary:hover {
    background-color: var(--color-neutral-300);
}

/* Upload Zone */
.upload-zone {
    border: 2px dashed var(--color-neutral-300);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    text-align: center;
    background-color: white;
    transition: all 0.2s ease;
    cursor: pointer;
}

.upload-zone:hover {
    border-color: var(--color-primary);
    background-color: var(--color-neutral-100);
}

.upload-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-md);
}

.upload-icon {
    width: 48px;
    height: 48px;
    color: var(--color-neutral-400);
}

/* Signature Pad */
.signature-container {
    background-color: white;
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
}

.signature-tabs {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.tab-btn {
    padding: var(--spacing-sm) var(--spacing-lg);
    border: none;
    background: none;
    color: var(--color-neutral-600);
    cursor: pointer;
    border-bottom: 2px solid transparent;
}

.tab-btn.active {
    color: var(--color-primary);
    border-bottom-color: var(--color-primary);
}

#signaturePad {
    width: 100%;
    height: 200px;
    border: 1px solid var(--color-neutral-300);
    border-radius: var(--border-radius-md);
    touch-action: none;
}

.signature-controls {
    display: flex;
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

/* PDF Preview */
.preview-container {
    background-color: white;
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-md);
}

.pdf-controls {
    display: flex;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.pdf-preview {
    min-height: 500px;
    border: 1px solid var(--color-neutral-300);
    border-radius: var(--border-radius-md);
    overflow: auto;
}

/* Footer */
.main-footer {
    margin-top: auto;
    background-color: white;
    padding: var(--spacing-lg) 0;
    text-align: center;
    color: var(--color-neutral-600);
    box-shadow: var(--shadow-sm);
}

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

/* Responsive Design */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }
    
    .section {
        padding: var(--spacing-lg) 0;
    }
    
    .upload-zone {
        padding: var(--spacing-lg);
    }
    
    .signature-container,
    .preview-container {
        padding: var(--spacing-md);
    }
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.fade-in {
    animation: fadeIn 0.3s ease-in-out;
}