/* ===== CSS Reset & Variables ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* Color Palette */
    --primary-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --secondary-gradient: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --success-gradient: linear-gradient(135deg, #4facfe 0%, #00f2fe 100%);
    --dark-bg: #0f0f1e;
    --card-bg: rgba(255, 255, 255, 0.05);
    --card-border: rgba(255, 255, 255, 0.1);
    --text-primary: #ffffff;
    --text-secondary: rgba(255, 255, 255, 0.7);
    --text-muted: rgba(255, 255, 255, 0.5);
    --input-bg: rgba(255, 255, 255, 0.08);
    --input-border: rgba(255, 255, 255, 0.15);
    --hover-bg: rgba(255, 255, 255, 0.1);
    
    /* Spacing */
    --spacing-xs: 0.5rem;
    --spacing-sm: 0.75rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    --font-size-sm: 0.875rem;
    --font-size-base: 1rem;
    --font-size-lg: 1.125rem;
    --font-size-xl: 1.5rem;
    --font-size-2xl: 2rem;
    --font-size-3xl: 2.5rem;
    
    /* Border Radius */
    --radius-sm: 0.5rem;
    --radius-md: 0.75rem;
    --radius-lg: 1rem;
    --radius-xl: 1.5rem;
    
    /* Shadows */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.3);
    --shadow-glow: 0 0 40px rgba(102, 126, 234, 0.4);
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;
}

/* ===== Base Styles ===== */
body {
    font-family: var(--font-family);
    background: var(--dark-bg);
    background-image: 
        radial-gradient(at 0% 0%, rgba(102, 126, 234, 0.2) 0px, transparent 50%),
        radial-gradient(at 100% 100%, rgba(118, 75, 162, 0.2) 0px, transparent 50%);
    color: var(--text-primary);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-lg);
    line-height: 1.6;
}

/* ===== Container ===== */
.container {
    max-width: 700px;
    width: 100%;
    animation: fadeIn 0.6s ease;
}

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

/* ===== Header ===== */
.header {
    text-align: center;
    margin-bottom: var(--spacing-2xl);
}

.title {
    font-size: var(--font-size-3xl);
    font-weight: 700;
    background: var(--primary-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-sm);
    letter-spacing: -0.02em;
}

.subtitle {
    font-size: var(--font-size-lg);
    color: var(--text-secondary);
    font-weight: 400;
}

/* ===== Calculator Card ===== */
.calculator-card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-xl);
    padding: var(--spacing-2xl);
    backdrop-filter: blur(20px);
    box-shadow: var(--shadow-lg), var(--shadow-glow);
    transition: transform var(--transition-base), box-shadow var(--transition-base);
}

.calculator-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg), 0 0 60px rgba(102, 126, 234, 0.5);
}

/* ===== Mode Selector ===== */
.mode-selector {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-xl);
}

.mode-btn {
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md) var(--spacing-sm);
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-xs);
}

.mode-icon {
    font-size: var(--font-size-xl);
}

.mode-text {
    font-size: var(--font-size-sm);
}

.mode-btn:hover {
    background: var(--hover-bg);
    border-color: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

.mode-btn.active {
    background: var(--primary-gradient);
    border-color: transparent;
    color: var(--text-primary);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

/* ===== Input Section ===== */
.input-section {
    margin-bottom: var(--spacing-xl);
}

.input-group {
    margin-bottom: var(--spacing-lg);
}

.input-label {
    display: block;
    font-size: var(--font-size-sm);
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-sm);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
}

.input-field {
    width: 100%;
    background: var(--input-bg);
    border: 2px solid var(--input-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-md) var(--spacing-lg);
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: var(--font-size-lg);
    font-weight: 600;
    transition: all var(--transition-base);
}

.input-field:focus {
    outline: none;
    border-color: #667eea;
    background: rgba(255, 255, 255, 0.1);
    box-shadow: 0 0 0 4px rgba(102, 126, 234, 0.2);
}

.input-field::placeholder {
    color: var(--text-muted);
    font-weight: 400;
}

.currency-symbol {
    position: absolute;
    left: var(--spacing-md);
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text-secondary);
    pointer-events: none;
}

.input-wrapper:has(.currency-symbol) .input-field {
    padding-left: 2.5rem;
}

.percent-symbol {
    position: absolute;
    right: var(--spacing-md);
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text-secondary);
    pointer-events: none;
}

.input-wrapper:has(.percent-symbol) .input-field {
    padding-right: 2.5rem;
}

/* ===== Quick Rates ===== */
.quick-rates {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.quick-rates-label {
    font-size: var(--font-size-sm);
    color: var(--text-muted);
    font-weight: 500;
}

.rate-btn {
    background: var(--input-bg);
    border: 1px solid var(--input-border);
    border-radius: var(--radius-sm);
    padding: var(--spacing-xs) var(--spacing-md);
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: var(--font-size-sm);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.rate-btn:hover {
    background: var(--success-gradient);
    border-color: transparent;
    color: var(--text-primary);
    transform: scale(1.05);
}

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

/* ===== Results Section ===== */
.results-section {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-lg);
    padding: var(--spacing-xl);
    margin-bottom: var(--spacing-xl);
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.result-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: rgba(255, 255, 255, 0.03);
    border-radius: var(--radius-md);
    transition: all var(--transition-base);
}

.result-item:hover {
    background: rgba(255, 255, 255, 0.06);
    transform: translateX(4px);
}

.result-item.highlight {
    background: linear-gradient(135deg, rgba(79, 172, 254, 0.15) 0%, rgba(0, 242, 254, 0.15) 100%);
    border: 1px solid rgba(79, 172, 254, 0.3);
}

.result-item.total {
    background: var(--primary-gradient);
    padding: var(--spacing-lg);
    box-shadow: 0 4px 16px rgba(102, 126, 234, 0.3);
}

.result-label {
    font-size: var(--font-size-sm);
    color: var(--text-secondary);
    font-weight: 500;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.result-item.total .result-label {
    color: var(--text-primary);
    font-weight: 700;
}

.result-value {
    font-size: var(--font-size-xl);
    font-weight: 700;
    color: var(--text-primary);
    font-variant-numeric: tabular-nums;
}

.result-divider {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 1.5rem;
}

.divider-icon {
    font-size: var(--font-size-lg);
    color: var(--text-muted);
    font-weight: 700;
}

/* ===== Breakdown Section ===== */
.breakdown-section {
    background: rgba(0, 0, 0, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: var(--radius-lg);
    padding: var(--spacing-lg);
}

.breakdown-title {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--spacing-md);
}

.breakdown-content {
    color: var(--text-secondary);
    font-size: var(--font-size-base);
    line-height: 1.8;
}

.breakdown-text {
    margin-bottom: var(--spacing-sm);
    font-family: 'Courier New', monospace;
    color: var(--text-secondary);
}

.breakdown-formula {
    background: rgba(255, 255, 255, 0.05);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: var(--radius-sm);
    border-left: 3px solid #667eea;
    margin: var(--spacing-sm) 0;
    font-family: 'Courier New', monospace;
    color: #4facfe;
}

/* ===== Footer ===== */
.footer {
    text-align: center;
    margin-top: var(--spacing-2xl);
    padding-top: var(--spacing-xl);
    color: var(--text-muted);
    font-size: var(--font-size-sm);
}

/* ===== Animations ===== */
@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-item {
    animation: slideIn 0.4s ease;
}

/* ===== Responsive Design ===== */
@media (max-width: 640px) {
    :root {
        --font-size-3xl: 2rem;
        --font-size-2xl: 1.5rem;
        --font-size-xl: 1.25rem;
    }
    
    .calculator-card {
        padding: var(--spacing-lg);
    }
    
    .mode-selector {
        grid-template-columns: 1fr;
    }
    
    .mode-btn {
        flex-direction: row;
        justify-content: center;
        padding: var(--spacing-md);
    }
    
    .quick-rates {
        justify-content: center;
    }
    
    .result-value {
        font-size: var(--font-size-lg);
    }
}

@media (max-width: 480px) {
    body {
        padding: var(--spacing-md);
    }
    
    .calculator-card {
        padding: var(--spacing-md);
    }
    
    .results-section,
    .breakdown-section {
        padding: var(--spacing-md);
    }
}