* {
    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;
    padding: 20px;
}

.container {
    max-width: 1600px;
    margin: 0 auto;
    background: white;
    border-radius: 12px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.2);
    overflow: hidden;
}

header {
    color: #333;
    padding: 30px;
    text-align: center;
}

header h1 {
    margin-bottom: 20px;
    font-size: 2em;
}

button {
    background: white;
    color: #667eea;
    border: none;
    padding: 12px 30px;
    margin: 0 10px;
    border-radius: 25px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.3);
}

button:active {
    transform: translateY(0);
}

.editor-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    padding: 30px;
    background: #f8f9fa;
}

.editor-panel {
    display: flex;
    flex-direction: column;
}

.editor-panel h2 {
    color: #333;
    margin-bottom: 15px;
    font-size: 1.2em;
}

textarea {
    width: 100%;
    height: 300px;
    padding: 15px;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-family: 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.5;
    resize: vertical;
    transition: border-color 0.3s ease;
}

textarea:focus {
    outline: none;
    border-color: #667eea;
}

.diff-container {
    padding: 30px;
    background: white;
}

.diff-container > h2 {
    color: #333;
    margin-bottom: 20px;
    font-size: 1.5em;
}

.diff-output {
    background: #f8f9fa;
    border-radius: 8px;
    overflow: auto;
}

.empty-state {
    color: #999;
    text-align: center;
    padding: 40px;
    font-style: italic;
}

/* diff2htmlのスタイルをカスタマイズ */
.diff-output .d2h-wrapper {
    border: 1px solid #e0e0e0;
    border-radius: 8px;
    overflow: hidden;
}

.diff-output .d2h-file-header {
    background: #f6f8fa;
    border-bottom: 1px solid #d0d7de;
    padding: 10px 15px;
}

.diff-output .d2h-code-side-line {
    font-family: 'Courier New', 'Monaco', monospace;
    font-size: 13px;
}

@media (max-width: 768px) {
    .editor-container {
        grid-template-columns: 1fr;
    }

    header h1 {
        font-size: 1.5em;
    }

    button {
        margin: 5px;
        padding: 10px 20px;
        font-size: 14px;
    }

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