:root {
    --primary-color: #6366f1;
    --secondary-color: #8b5cf6;
    --background: #ffffff;
    --surface: #f8fafc;
    --border: #e2e8f0;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --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);
    --radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 20px;
    color: var(--text-primary);
}

.container {
    width: 100%;
    max-width: 800px;
    background: var(--background);
    border-radius: 20px;
    box-shadow: var(--shadow-lg);
    overflow: hidden;
    animation: slideIn 0.5s ease-out;
}

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

header {
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    padding: 30px;
    text-align: center;
    position: relative;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 8px;
    letter-spacing: -0.5px;
}

.subtitle {
    font-size: 1.1rem;
    opacity: 0.95;
    font-weight: 400;
}

.lang-selector {
    position: absolute;
    top: 20px;
    right: 20px;
    display: flex;
    gap: 8px;
}

.lang-btn {
    padding: 6px 12px;
    background: rgba(255, 255, 255, 0.2);
    border: 1px solid rgba(255, 255, 255, 0.3);
    border-radius: 6px;
    color: white;
    cursor: pointer;
    font-size: 0.9rem;
    transition: var(--transition);
}

.lang-btn:hover {
    background: rgba(255, 255, 255, 0.3);
}

.lang-btn.active {
    background: rgba(255, 255, 255, 0.4);
    border-color: white;
}

main {
    padding: 30px;
}

.color-preview-section {
    margin-bottom: 30px;
}

.color-display {
    height: 200px;
    border-radius: var(--radius);
    background: #000000;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    overflow: hidden;
    box-shadow: var(--shadow-md);
    transition: var(--transition);
}

.color-info {
    text-align: center;
}

#currentColorText {
    font-size: 2rem;
    font-weight: 600;
    font-family: 'Courier New', monospace;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.converter-section {
    display: grid;
    gap: 25px;
}

.input-group {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.input-group label {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.95rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.input-wrapper {
    display: flex;
    gap: 10px;
    align-items: center;
}

input[type="text"],
input[type="number"] {
    flex: 1;
    padding: 12px 16px;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    font-family: 'Courier New', monospace;
    transition: var(--transition);
    background: var(--surface);
}

input[type="text"]:focus,
input[type="number"]:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

input[readonly] {
    background: var(--surface);
    cursor: default;
}

.rgb-inputs {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 15px;
    margin-bottom: 15px;
}

.rgb-input {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.rgb-input label {
    text-align: center;
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.rgb-input input[type="number"] {
    text-align: center;
    padding: 8px;
}

.slider {
    width: 100%;
    height: 6px;
    border-radius: 3px;
    background: var(--border);
    outline: none;
    -webkit-appearance: none;
    cursor: pointer;
}

.slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    transition: var(--transition);
}

.slider::-webkit-slider-thumb:hover {
    transform: scale(1.2);
    box-shadow: 0 0 0 8px rgba(99, 102, 241, 0.1);
}

.slider::-moz-range-thumb {
    width: 18px;
    height: 18px;
    border-radius: 50%;
    background: var(--primary-color);
    cursor: pointer;
    border: none;
    transition: var(--transition);
}

.copy-btn {
    padding: 10px;
    background: var(--surface);
    border: 2px solid var(--border);
    border-radius: 8px;
    cursor: pointer;
    color: var(--text-secondary);
    transition: var(--transition);
    display: flex;
    align-items: center;
    justify-content: center;
}

.copy-btn:hover {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
    transform: scale(1.05);
}

.picker-section {
    margin-top: 30px;
    padding-top: 30px;
    border-top: 1px solid var(--border);
}

.picker-section label {
    display: block;
    margin-bottom: 10px;
    font-weight: 600;
    color: var(--text-primary);
}

input[type="color"] {
    width: 100%;
    height: 60px;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
    background: var(--surface);
    transition: var(--transition);
}

input[type="color"]:hover {
    border-color: var(--primary-color);
}

.preset-section {
    margin-top: 30px;
    padding-top: 30px;
    border-top: 1px solid var(--border);
}

.preset-section h3 {
    margin-bottom: 15px;
    color: var(--text-primary);
    font-size: 1.1rem;
}

.preset-colors {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(60px, 1fr));
    gap: 10px;
}

.preset-color {
    aspect-ratio: 1;
    border-radius: 8px;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-sm);
    position: relative;
    overflow: hidden;
}

.preset-color::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(255,255,255,0.3) 0%, transparent 50%);
    opacity: 0;
    transition: opacity 0.3s;
}

.preset-color:hover {
    transform: scale(1.1);
    box-shadow: var(--shadow-md);
}

.preset-color:hover::before {
    opacity: 1;
}

.action-section {
    margin-top: 30px;
    text-align: center;
}

.random-btn {
    padding: 14px 32px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    box-shadow: var(--shadow-md);
}

.random-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.random-btn:active {
    transform: translateY(0);
}

footer {
    padding: 20px;
    text-align: center;
    background: var(--surface);
    border-top: 1px solid var(--border);
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.toast {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--text-primary);
    color: white;
    padding: 12px 24px;
    border-radius: 8px;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    transition: all 0.3s ease-out;
    z-index: 1000;
    pointer-events: none;
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

/* レスポンシブデザイン */
@media (max-width: 640px) {
    h1 {
        font-size: 2rem;
    }
    
    .subtitle {
        font-size: 1rem;
    }
    
    .lang-selector {
        position: static;
        margin-top: 20px;
        justify-content: center;
    }
    
    .rgb-inputs {
        grid-template-columns: 1fr;
    }
    
    .preset-colors {
        grid-template-columns: repeat(auto-fill, minmax(50px, 1fr));
    }
    
    main {
        padding: 20px;
    }
}