/* Apple UI Style - Modern, Clean, Minimalist */

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

:root {
    /* Apple-inspired Color Palette */
    --bg-primary: #f5f5f7;
    --bg-secondary: #ffffff;
    --text-primary: #1d1d1f;
    --text-secondary: #6e6e73;
    --text-tertiary: #86868b;
    --accent-blue: #007aff;
    --accent-blue-hover: #0051d5;
    --border-color: #d2d2d7;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-md: 0 4px 16px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 32px rgba(0, 0, 0, 0.12);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 18px;
    --radius-xl: 24px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'SF Pro Text', 'Helvetica Neue', Helvetica, Arial, sans-serif;
    background: var(--bg-primary);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    width: 100%;
    max-width: 560px;
}

.card {
    background: var(--bg-secondary);
    border-radius: var(--radius-xl);
    padding: 32px;
    box-shadow: var(--shadow-md);
    animation: fadeIn 0.6s cubic-bezier(0.16, 1, 0.3, 1);
    backdrop-filter: blur(20px);
}

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

h1 {
    color: var(--text-primary);
    text-align: center;
    margin-bottom: 8px;
    font-size: 32px;
    font-weight: 600;
    letter-spacing: -0.5px;
}

.subtitle {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 32px;
    font-size: 17px;
    font-weight: 400;
}

.converter-box {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.currency-selectors {
    display: flex;
    flex-direction: row;
    gap: 12px;
    align-items: flex-end;
}

.select-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
    flex: 1;
    min-width: 0;
}

.select-group label {
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 13px;
    letter-spacing: -0.08px;
    padding-left: 2px;
}

.currency-select {
    width: 100%;
    padding: 12px 16px;
    padding-right: 36px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 17px;
    font-weight: 400;
    background: var(--bg-secondary);
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    outline: none;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6' viewBox='0 0 10 6'%3E%3Cpath fill='%236e6e73' d='M5 6L0 0h10z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    background-size: 10px;
    box-sizing: border-box;
}

.currency-select:hover {
    border-color: var(--text-tertiary);
    background-color: #fafafa;
}

.currency-select:focus {
    border-color: var(--accent-blue);
    background-color: var(--bg-secondary);
    box-shadow: 0 0 0 4px rgba(0, 122, 255, 0.1);
}

.swap-button-container {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-shrink: 0;
}

.swap-btn {
    width: 44px;
    height: 44px;
    min-width: 44px;
    border-radius: 50%;
    border: 1.5px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-secondary);
    font-size: 20px;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    align-items: center;
    justify-content: center;
    outline: none;
    -webkit-tap-highlight-color: transparent;
}

.swap-btn:hover {
    background: var(--accent-blue);
    color: white;
    border-color: var(--accent-blue);
    transform: rotate(180deg) scale(1.05);
}

.swap-btn:active {
    transform: rotate(180deg) scale(0.95);
    background: var(--accent-blue-hover);
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.input-group label {
    color: var(--text-secondary);
    font-weight: 500;
    font-size: 13px;
    letter-spacing: -0.08px;
    padding-left: 2px;
}

.input-group input {
    width: 100%;
    padding: 14px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 34px;
    font-weight: 400;
    color: var(--text-primary);
    background: var(--bg-secondary);
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    outline: none;
    -webkit-appearance: none;
    appearance: none;
}

.input-group input::placeholder {
    color: var(--text-tertiary);
    font-size: 34px;
}

.input-group input:hover {
    border-color: var(--text-tertiary);
    background-color: #fafafa;
}

.input-group input:focus {
    border-color: var(--accent-blue);
    background-color: var(--bg-secondary);
    box-shadow: 0 0 0 4px rgba(0, 122, 255, 0.1);
}

.result {
    padding: 24px;
    background: linear-gradient(135deg, #f8f9fa 0%, #e9ecef 100%);
    border-radius: var(--radius-md);
    text-align: center;
    animation: slideIn 0.3s cubic-bezier(0.16, 1, 0.3, 1);
    border: 1px solid rgba(0, 0, 0, 0.05);
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-label {
    color: var(--text-secondary);
    font-size: 13px;
    font-weight: 500;
    margin-bottom: 8px;
    letter-spacing: -0.08px;
}

.result-value {
    color: var(--text-primary);
    font-size: 36px;
    font-weight: 600;
    margin-bottom: 8px;
    letter-spacing: -0.5px;
}

.exchange-rate {
    color: var(--text-secondary);
    font-size: 15px;
    font-weight: 400;
}

.loading {
    text-align: center;
    padding: 32px 20px;
}

.spinner {
    border: 3px solid #f0f0f0;
    border-top: 3px solid var(--accent-blue);
    border-radius: 50%;
    width: 32px;
    height: 32px;
    animation: spin 0.8s linear infinite;
    margin: 0 auto 16px;
}

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

.loading p {
    color: var(--text-secondary);
    font-size: 15px;
    font-weight: 400;
}

.error {
    padding: 16px;
    background: #fff5f5;
    color: #d70015;
    border-radius: var(--radius-md);
    text-align: center;
    border: 1px solid #ffebee;
    font-size: 15px;
    font-weight: 400;
}

.hidden {
    display: none;
}

.info {
    margin-top: 24px;
    text-align: center;
    color: var(--text-secondary);
    font-size: 13px;
    font-weight: 400;
}

.info p {
    letter-spacing: -0.08px;
}

/* Mobile Optimizations */
@media (max-width: 768px) {
    body {
        padding: 16px;
        align-items: flex-start;
        padding-top: 24px;
    }
    
    .container {
        max-width: 100%;
    }
    
    .card {
        padding: 24px 20px;
        border-radius: var(--radius-lg);
    }
    
    h1 {
        font-size: 28px;
        margin-bottom: 6px;
    }
    
    .subtitle {
        font-size: 15px;
        margin-bottom: 24px;
    }
    
    .converter-box {
        gap: 20px;
    }
    
    .currency-selectors {
        flex-direction: column;
        gap: 16px;
        align-items: stretch;
    }
    
    .swap-button-container {
        justify-content: center;
    }
    
    .swap-btn {
        width: 40px;
        height: 40px;
        min-width: 40px;
        font-size: 18px;
    }
    
    .currency-select {
        padding: 14px 16px;
        padding-right: 36px;
        font-size: 16px;
    }
    
    .input-group input {
        font-size: 32px;
        padding: 16px;
    }
    
    .input-group input::placeholder {
        font-size: 28px;
    }
    
    .result {
        padding: 20px;
    }
    
    .result-value {
        font-size: 32px;
    }
    
    .exchange-rate {
        font-size: 14px;
    }
}

/* Small Mobile Devices */
@media (max-width: 375px) {
    .card {
        padding: 20px 16px;
    }
    
    h1 {
        font-size: 24px;
    }
    
    .subtitle {
        font-size: 14px;
    }
    
    .input-group input {
        font-size: 28px;
    }
    
    .input-group input::placeholder {
        font-size: 24px;
    }
    
    .result-value {
        font-size: 28px;
    }
}

/* Touch-friendly interactions for mobile */
@media (hover: none) and (pointer: coarse) {
    .currency-select:active,
    .swap-btn:active {
        transform: scale(0.97);
    }
}

/* Dark mode support (optional - for future) */
@media (prefers-color-scheme: dark) {
    :root {
        --bg-primary: #000000;
        --bg-secondary: #1c1c1e;
        --text-primary: #ffffff;
        --text-secondary: #98989d;
        --text-tertiary: #636366;
        --border-color: #38383a;
    }
    
    .card {
        background: var(--bg-secondary);
    }
    
    .result {
        background: linear-gradient(135deg, #2c2c2e 0%, #1c1c1e 100%);
        border-color: rgba(255, 255, 255, 0.1);
    }
    
    .error {
        background: #2a1a1a;
        border-color: #3a2525;
    }
    
    .currency-select:hover,
    .input-group input:hover {
        background-color: #2c2c2e;
    }
}