/* ===== CSS VARIABLES ===== */
:root {
    /* Color Palette */
    --primary-blue: #2196F3;
    --success-green: #4CAF50;
    --warning-yellow: #FFC107;
    --error-red: #F44336;
    --accent-purple: #9C27B0;
    
    /* Handmade/Sketch Style Colors */
    --sketch-dark: #2c3e50;
    --sketch-light: #ecf0f1;
    --sketch-gray: #95a5a6;
    --sketch-white: #ffffff;
    
    /* Typography */
    --font-primary: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    --font-handwritten: 'Comic Sans MS', cursive, sans-serif;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    
    /* Border Radius */
    --border-radius-sm: 8px;
    --border-radius-md: 12px;
    --border-radius-lg: 16px;
    
    /* Shadows */
    --shadow-light: 0 2px 4px rgba(0, 0, 0, 0.1);
    --shadow-medium: 0 4px 8px rgba(0, 0, 0, 0.15);
    --shadow-heavy: 0 8px 16px rgba(0, 0, 0, 0.2);
    
    /* Sketch Effects */
    --sketch-border: 2px solid var(--sketch-dark);
    --sketch-border-dashed: 2px dashed var(--sketch-gray);
}

/* ===== GLOBAL STYLES ===== */
* {
    box-sizing: border-box;
}

body {
    font-family: var(--font-primary);
    background: linear-gradient(135deg, var(--sketch-light) 0%, var(--sketch-white) 100%);
    color: var(--sketch-dark);
    line-height: 1.6;
    overflow-x: hidden;
}

/* Add subtle paper texture */
body::before {
    content: '';
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-image: 
        radial-gradient(circle at 1px 1px, rgba(0,0,0,0.05) 1px, transparent 0);
    background-size: 20px 20px;
    pointer-events: none;
    z-index: -1;
}

/* ===== HEADER STYLES ===== */
.app-title {
    font-family: var(--font-handwritten);
    font-size: 3rem;
    font-weight: bold;
    color: var(--primary-blue);
    text-shadow: 2px 2px 0px var(--sketch-gray);
    margin-bottom: var(--spacing-sm);
    position: relative;
}

.app-title::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 50%;
    transform: translateX(-50%);
    width: 80%;
    height: 3px;
    background: var(--warning-yellow);
    border-radius: 2px;
    transform: translateX(-50%) rotate(-1deg);
}

.app-subtitle {
    font-size: 1.1rem;
    color: var(--sketch-gray);
    margin-bottom: 0;
    font-style: italic;
}

/* ===== CONVERTER CONTAINER ===== */
.converter-container {
    width: 100%;
    max-width: 500px;
    padding: var(--spacing-md);
}

.converter-card {
    background: var(--sketch-white);
    border: var(--sketch-border);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-xl);
    box-shadow: var(--shadow-medium);
    position: relative;
    transform: rotate(-0.5deg);
    transition: all 0.3s ease;
}

.converter-card::before {
    content: '';
    position: absolute;
    top: -5px;
    left: -5px;
    right: -5px;
    bottom: -5px;
    background: var(--accent-purple);
    border-radius: var(--border-radius-lg);
    z-index: -1;
    opacity: 0.1;
    transform: rotate(1deg);
}

.converter-card:hover {
    transform: rotate(0deg);
    box-shadow: var(--shadow-heavy);
}

/* ===== FORM STYLES ===== */
.form-label {
    font-weight: 600;
    color: var(--sketch-dark);
    margin-bottom: var(--spacing-sm);
    font-size: 0.95rem;
}

.temperature-input,
.unit-select {
    border: var(--sketch-border);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    font-size: 1rem;
    transition: all 0.3s ease;
    background: var(--sketch-white);
}

.temperature-input:focus,
.unit-select:focus {
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 0.2rem rgba(33, 150, 243, 0.25);
    outline: none;
    transform: translateY(-1px);
}

.input-group-text {
    border: var(--sketch-border);
    border-left: none;
    background: var(--success-green);
    color: var(--sketch-white);
    font-weight: bold;
    border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
}

/* ===== BUTTON STYLES ===== */
.convert-btn {
    background: linear-gradient(135deg, var(--primary-blue) 0%, var(--accent-purple) 100%);
    border: var(--sketch-border);
    color: var(--sketch-white);
    font-size: 1.1rem;
    font-weight: bold;
    padding: var(--spacing-md) var(--spacing-xl);
    border-radius: var(--border-radius-md);
    transition: all 0.3s ease;
    position: relative;
    overflow: hidden;
    min-width: 150px;
}

.convert-btn::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.2), transparent);
    transition: left 0.5s;
}

.convert-btn:hover {
    transform: translateY(-2px) rotate(1deg);
    box-shadow: var(--shadow-heavy);
    background: linear-gradient(135deg, var(--accent-purple) 0%, var(--primary-blue) 100%);
}

.convert-btn:hover::before {
    left: 100%;
}

.convert-btn:active {
    transform: translateY(0px) rotate(0deg);
}

.btn-text {
    margin-right: var(--spacing-sm);
}

.btn-icon {
    font-size: 1.2em;
}

/* Quick Convert Buttons */
.quick-convert {
    font-size: 0.75rem;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    transition: all 0.2s ease;
    width: 100%;
}

.quick-convert:hover {
    background: var(--primary-blue);
    color: var(--sketch-white);
    border-color: var(--primary-blue);
    transform: translateY(-1px);
}

/* ===== RESULT STYLES ===== */
.result-section,
.error-section {
    animation: slideInUp 0.5s ease-out;
}

@keyframes slideInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-alert {
    background: linear-gradient(135deg, var(--success-green) 0%, var(--primary-blue) 100%);
    border: var(--sketch-border);
    border-radius: var(--border-radius-md);
    color: var(--sketch-white);
    padding: var(--spacing-lg);
    margin-bottom: 0;
    position: relative;
    overflow: hidden;
}

.result-alert::before {
    content: '✓';
    position: absolute;
    top: 10px;
    right: 15px;
    font-size: 1.5rem;
    opacity: 0.3;
}

.result-title {
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    opacity: 0.9;
}

.result-value {
    font-size: 1.8rem;
    font-weight: bold;
    margin-bottom: var(--spacing-sm);
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.3);
}

.result-details {
    font-size: 0.85rem;
    opacity: 0.8;
    font-style: italic;
}

/* ===== ERROR STYLES ===== */
.error-alert {
    background: linear-gradient(135deg, var(--error-red) 0%, var(--warning-yellow) 100%);
    border: var(--sketch-border);
    border-radius: var(--border-radius-md);
    color: var(--sketch-white);
    padding: var(--spacing-lg);
    margin-bottom: 0;
    position: relative;
}

.error-title {
    font-size: 1rem;
    font-weight: bold;
    margin-bottom: var(--spacing-sm);
}

.error-message {
    font-size: 0.9rem;
    opacity: 0.9;
}

/* ===== EXAMPLES SECTION ===== */
.examples-section {
    border-top: var(--sketch-border-dashed);
    padding-top: var(--spacing-lg);
    margin-top: var(--spacing-lg);
}

.examples-title {
    color: var(--sketch-gray);
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    text-align: center;
}

/* ===== FOOTER STYLES ===== */
.footer {
    background: var(--sketch-dark);
    color: var(--sketch-light);
    margin-top: auto;
    border-top: 3px solid var(--primary-blue);
}

.footer-text {
    font-size: 0.85rem;
}

.footer-link {
    color: var(--primary-blue);
    text-decoration: none;
    font-weight: 600;
    transition: color 0.3s ease;
}

.footer-link:hover {
    color: var(--warning-yellow);
    text-decoration: underline;
}

/* ===== VALIDATION STYLES ===== */
.is-invalid {
    border-color: var(--error-red) !important;
    box-shadow: 0 0 0 0.2rem rgba(244, 67, 54, 0.25) !important;
}

.invalid-feedback {
    display: none;
    color: var(--error-red);
    font-size: 0.85rem;
    margin-top: var(--spacing-xs);
}

.is-invalid ~ .invalid-feedback {
    display: block;
}

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 768px) {
    .app-title {
        font-size: 2.5rem;
    }
    
    .converter-container {
        padding: var(--spacing-sm);
    }
    
    .converter-card {
        padding: var(--spacing-lg);
        transform: none;
    }
    
    .converter-card:hover {
        transform: none;
    }
    
    .result-value {
        font-size: 1.5rem;
    }
    
    .quick-convert {
        font-size: 0.7rem;
        padding: var(--spacing-xs);
    }
}

@media (max-width: 576px) {
    .app-title {
        font-size: 2rem;
    }
    
    .app-subtitle {
        font-size: 1rem;
    }
    
    .converter-card {
        padding: var(--spacing-md);
    }
    
    .convert-btn {
        font-size: 1rem;
        padding: var(--spacing-sm) var(--spacing-lg);
        min-width: 120px;
    }
    
    .result-value {
        font-size: 1.3rem;
    }
}

/* ===== ACCESSIBILITY IMPROVEMENTS ===== */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* Focus indicators for keyboard navigation */
.convert-btn:focus,
.quick-convert:focus,
.temperature-input:focus,
.unit-select:focus {
    outline: 2px solid var(--primary-blue);
    outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
    :root {
        --sketch-dark: #000000;
        --sketch-light: #ffffff;
        --sketch-gray: #666666;
    }
    
    .converter-card {
        border-width: 3px;
    }
    
    .temperature-input,
    .unit-select {
        border-width: 2px;
    }
}

/* Print styles */
@media print {
    .footer,
    .examples-section,
    .convert-btn {
        display: none !important;
    }
    
    .converter-card {
        box-shadow: none;
        border: 1px solid #000;
    }
    
    body {
        background: white;
    }
}