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

:root {
    --primary-color: #0052CC;
    --primary-hover: #0747A6;
    --success-color: #00875A;
    --danger-color: #DE350B;
    --warning-color: #FF8B00;
    --background: #FAFBFC;
    --surface: #FFFFFF;
    --text-primary: #172B4D;
    --text-secondary: #5E6C84;
    --border: #DFE1E6;
    --added-bg: #E3FCEF;
    --added-border: #ABF5D1;
    --deleted-bg: #FFEBE6;
    --deleted-border: #FF8F73;
    --changed-bg: #FFF0B3;
    --changed-border: #FFE380;
    --unchanged-bg: #F4F5F7;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    flex: 1;
    display: flex;
    flex-direction: column;
}

header {
    padding: 40px 0 30px;
    text-align: center;
    position: relative;
}

h1 {
    font-size: 2.5rem;
    font-weight: 600;
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
}

.icon {
    font-size: 3rem;
}

.subtitle {
    font-size: 1.1rem;
    color: var(--text-secondary);
}

.language-selector {
    position: absolute;
    top: 20px;
    right: 0;
}

#languageSelect {
    padding: 8px 16px;
    border: 1px solid var(--border);
    border-radius: 8px;
    background: var(--surface);
    font-size: 14px;
    color: var(--text-primary);
    cursor: pointer;
    transition: all 0.2s;
}

#languageSelect:hover {
    border-color: var(--primary-color);
}

main {
    flex: 1;
    padding-bottom: 60px;
}

.file-input-section {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-bottom: 30px;
}

.file-input-wrapper {
    background: var(--surface);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    transition: transform 0.2s, box-shadow 0.2s;
}

.file-input-wrapper:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

.file-label {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.1rem;
    font-weight: 500;
    margin-bottom: 15px;
}

.file-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 30px;
    height: 30px;
    background: var(--primary-color);
    color: white;
    border-radius: 50%;
    font-size: 0.9rem;
}

.file-input-container {
    position: relative;
}

input[type="file"] {
    position: absolute;
    opacity: 0;
    width: 100%;
    height: 100%;
    cursor: pointer;
}

.file-input-button {
    display: inline-block;
    padding: 10px 20px;
    background: var(--primary-color);
    color: white;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.2s;
    font-weight: 500;
}

.file-input-button:hover {
    background: var(--primary-hover);
}

.file-name {
    display: block;
    margin-top: 10px;
    color: var(--text-secondary);
    font-size: 0.9rem;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.action-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-bottom: 40px;
}

.compare-button, .clear-button {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 30px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

.compare-button {
    background: var(--success-color);
    color: white;
}

.compare-button:hover:not(:disabled) {
    background: #006644;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 135, 90, 0.3);
}

.compare-button:disabled {
    background: var(--border);
    color: var(--text-secondary);
    cursor: not-allowed;
    transform: none;
}

.clear-button {
    background: transparent;
    color: var(--danger-color);
    border: 2px solid var(--danger-color);
}

.clear-button:hover {
    background: var(--danger-color);
    color: white;
}

.button-icon {
    font-size: 1.2rem;
}

.stats-section {
    display: flex;
    gap: 20px;
    justify-content: center;
    margin-bottom: 40px;
}

.stat-card {
    background: var(--surface);
    padding: 20px 40px;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.stat-number {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 5px;
}

.stat-card:nth-child(1) .stat-number { color: var(--success-color); }
.stat-card:nth-child(2) .stat-number { color: var(--danger-color); }
.stat-card:nth-child(3) .stat-number { color: var(--warning-color); }

.stat-label {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.comparison-result {
    background: var(--surface);
    padding: 30px;
    border-radius: 12px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
}

.comparison-result h2 {
    margin-bottom: 20px;
    font-size: 1.5rem;
}

.diff-container {
    font-family: 'Consolas', 'Monaco', 'Courier New', monospace;
    font-size: 14px;
    line-height: 1.5;
}

.diff-line {
    display: grid;
    grid-template-columns: 80px 30px 1fr;
    align-items: start;
    padding: 8px;
    border-bottom: 1px solid var(--border);
    transition: background 0.2s;
}

.diff-line:hover {
    background: var(--background);
}

.diff-line.added {
    background: var(--added-bg);
    border-left: 4px solid var(--success-color);
}

.diff-line.deleted {
    background: var(--deleted-bg);
    border-left: 4px solid var(--danger-color);
}

.diff-line.changed {
    background: var(--changed-bg);
    border-left: 4px solid var(--warning-color);
}

.diff-line.unchanged {
    background: var(--unchanged-bg);
    opacity: 0.7;
}

.line-number {
    color: var(--text-secondary);
    font-size: 12px;
    text-align: right;
    padding-right: 10px;
}

.diff-indicator {
    text-align: center;
    font-weight: bold;
}

.diff-line.added .diff-indicator { color: var(--success-color); }
.diff-line.deleted .diff-indicator { color: var(--danger-color); }
.diff-line.changed .diff-indicator { color: var(--warning-color); }

.line-content {
    white-space: pre-wrap;
    word-break: break-word;
}

.old-content {
    color: var(--danger-color);
    text-decoration: line-through;
    margin-bottom: 4px;
}

.new-content {
    color: var(--success-color);
}

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

/* レスポンシブデザイン */
@media (max-width: 768px) {
    .file-input-section {
        grid-template-columns: 1fr;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    .icon {
        font-size: 2.5rem;
    }
    
    .stats-section {
        flex-direction: column;
    }
    
    .stat-card {
        width: 100%;
    }
    
    .diff-line {
        grid-template-columns: 60px 20px 1fr;
        font-size: 12px;
    }
    
    .language-selector {
        position: static;
        margin-top: 20px;
    }
}