:root {
    --text-color: #e0e0e0;
    --bg-color: #121212;
    --panel-bg: #1e1e1e;
    --border-color: #333333;
    --highlight-color: #2a2a2a;
    --accent-color: #bbbbbb;
    --quote-color: #888888;
    --error-color: #777777;
    --btn-bg: #333333;
    --btn-hover: #444444;
    --selected-color: #2a4a7a;
    --thread-line: #555555;
    --thread-line-active: #777777;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    line-height: 1.5;
    color: var(--text-color);
    background-color: var(--bg-color);
    font-size: 15px;
    height: 100vh;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.header {
    background-color: var(--panel-bg);
    padding: 8px 15px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-shrink: 0;
}

.header h1 {
    font-size: 1.1rem;
    color: var(--text-color);
}

.thread-title-header {
    display: flex;
    flex-direction: column;
    gap: 4px;
}

.thread-url-link {
    font-size: 0.75rem;
    color: var(--quote-color);
    text-decoration: none;
    opacity: 0.8;
    transition: opacity 0.2s, color 0.2s;
}

.thread-url-link:hover {
    opacity: 1;
    color: #4a9eff;
    text-decoration: underline;
}

.nav-controls {
    display: flex;
    gap: 8px;
    align-items: center;
}

.nav-button {
    background: var(--btn-bg);
    color: var(--text-color);
    border: 1px solid var(--border-color);
    padding: 4px 12px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: background-color 0.2s;
}

.nav-button:hover {
    background-color: var(--btn-hover);
}

.nav-button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.view-toggle {
    background: var(--accent-color);
    color: var(--bg-color);
    border: none;
    padding: 4px 12px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 0.9rem;
    font-weight: bold;
}

.view-toggle.active {
    background: var(--selected-color);
    color: var(--text-color);
}

.main-container {
    flex: 1;
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.breadcrumb {
    display: flex;
    align-items: center;
    padding: 8px 15px;
    font-size: 0.85rem;
    flex-wrap: wrap;
    border-bottom: 1px solid var(--border-color);
    background-color: var(--panel-bg);
    flex-shrink: 0;
}

.breadcrumb-item {
    color: var(--accent-color);
    cursor: pointer;
    margin: 2px 0;
    text-decoration: underline;
}

.breadcrumb-separator {
    margin: 0 5px;
    color: var(--text-color);
}

.content-area {
    flex: 1;
    overflow-y: auto;
    background-color: var(--bg-color);
}

.content-header {
    padding: 15px;
    background-color: var(--panel-bg);
    border-bottom: 1px solid var(--border-color);
    font-weight: bold;
    color: var(--text-color);
    position: sticky;
    top: 0;
    z-index: 10;
}

.list {
    list-style: none;
}

.list-item {
    display: flex;
    flex-direction: column;
    padding: 8px 15px;
    color: var(--text-color);
    text-decoration: none;
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    transition: background-color 0.2s;
    font-size: 0.9rem;
}

.list-item:hover {
    background-color: var(--highlight-color);
}

.list-item.selected {
    background-color: var(--selected-color);
}

/* 既読スレッドの強調表示スタイル */
.list-item.read {
    opacity: 1; /* 透明度を戻す */
    background: linear-gradient(135deg, #2a2a2a 0%, #1a1a1a 100%); /* グラデーション背景 */
    border-left: 4px solid #4a9eff; /* 青い左ボーダー */
    position: relative;
    overflow: hidden;
}

.list-item.read::before {
    content: "✓";
    position: absolute;
    top: 50%;
    right: 15px;
    transform: translateY(-50%);
    color: #4a9eff;
    font-size: 1.2rem;
    font-weight: bold;
}

.list-item.read .thread-number {
    color: #4a9eff; /* 青色で目立たせる */
    background: rgba(74, 158, 255, 0.2);
    padding: 2px 6px;
    border-radius: 3px;
    font-weight: bold;
}

.list-item.read .thread-title-container {
    padding-right: 35px; /* チェックマークのスペースを確保 */
}

.list-item.read:hover {
    opacity: 1;
    background: linear-gradient(135deg, #3a3a3a 0%, #2a2a2a 100%);
    border-left-color: #6bb6ff;
}

.list-item.read:hover::before {
    color: #6bb6ff;
}

/* 既読マークのテキスト表示も強化 */
.list-item.read .read-mark {
    color: #4a9eff;
    font-size: 0.85rem;
    font-weight: bold;
    background: rgba(74, 158, 255, 0.2);
    padding: 2px 6px;
    border-radius: 10px;
    margin-left: 10px;
    border: 1px solid rgba(74, 158, 255, 0.3);
}

.thread-number {
    font-weight: bold;
    color: var(--accent-color);
    margin-right: 8px;
    min-width: 30px;
    font-size: 0.85rem;
}

.thread-title-container {
    display: flex;
    align-items: flex-start;
}

.category-header {
    font-weight: bold;
    padding: 8px 15px;
    background-color: var(--highlight-color);
    border-bottom: 1px solid var(--border-color);
    color: var(--text-color);
    font-size: 0.9rem;
}

.welcome-message {
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100%;
    color: var(--quote-color);
    font-size: 1.1rem;
    text-align: center;
    padding: 40px;
}

/* ツリー構造のスタイル */
.thread-tree {
    padding: 10px 0;
}

.post {
    background-color: var(--panel-bg);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    margin: 5px 0;
    position: relative;
}

.post.root-post {
    margin-left: 15px;
    margin-right: 15px;
}

.post.reply-post {
    margin-left: calc(40px + var(--reply-depth, 0) * 30px);
    margin-right: 15px;
    border-left: 3px solid var(--thread-line);
}

.post.reply-post::before {
    content: '';
    position: absolute;
    left: -20px;
    top: 20px;
    width: 17px;
    height: 2px;
    background-color: var(--thread-line);
}

.post.reply-post.has-continue-line::after {
    content: '';
    position: absolute;
    left: -20px;
    top: 0;
    bottom: 0;
    width: 2px;
    background-color: var(--thread-line);
}

.post-content {
    padding: 12px;
}

.post-header-5ch {
    margin-bottom: 8px;
    padding: 6px 8px;
    border-bottom: 1px solid var(--border-color);
    font-size: 0.75rem;
    color: var(--text-color);
    font-family: 'MS PGothic', 'Hiragino Kaku Gothic Pro', sans-serif;
    line-height: 1.3;
    background-color: var(--highlight-color);
    border-radius: 2px;
}

.post-body {
    white-space: pre-wrap;
    word-wrap: break-word;
    line-height: 1.6;
    font-size: 15px;
}

.post-ref {
    color: var(--quote-color);
    text-decoration: none;
    font-weight: bold;
}

.post-ref:hover {
    text-decoration: underline;
}

.post-ref.invalid {
    opacity: 0.5;
    text-decoration: line-through;
    cursor: not-allowed;
}

.post:target {
    animation: highlight 1.5s ease;
    border-left: 3px solid var(--accent-color) !important;
}

.post.highlighted {
    border-left: 3px solid var(--accent-color) !important;
    --thread-line: var(--thread-line-active);
}

@keyframes highlight {
    0% { background-color: rgba(187, 187, 187, 0.2); }
    100% { background-color: transparent; }
}

.error-message {
    color: var(--error-color);
    padding: 15px;
    border-radius: 4px;
    border-left: 3px solid var(--error-color);
    background-color: rgba(119, 119, 119, 0.1);
    margin: 15px;
}

.loading {
    display: inline-block;
    width: 20px;
    height: 20px;
    border: 3px solid rgba(85, 85, 85, 0.3);
    border-radius: 50%;
    border-top-color: var(--accent-color);
    animation: spin 1s ease-in-out infinite;
    margin-right: 10px;
    vertical-align: middle;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.board-color-1 { border-left: 3px solid #555555; }
.board-color-2 { border-left: 3px solid #777777; }
.board-color-3 { border-left: 3px solid #999999; }
.board-color-4 { border-left: 3px solid #666666; }
.board-color-5 { border-left: 3px solid #888888; }
.board-color-6 { border-left: 3px solid #444444; }

.external-link {
    color: #4a9eff;
    text-decoration: underline;
}

.external-link:hover {
    color: #6bb6ff;
}

.media-link {
    color: #ff9500;
    text-decoration: underline;
    font-weight: bold;
}

.media-link:hover {
    color: #ffb340;
}

.video-link {
    color: #ff6b6b;
}

.video-link:hover {
    color: #ff8e8e;
}

.image-link {
    color: #51cf66;
}

.content-area::-webkit-scrollbar {
    width: 8px;
}

.content-area::-webkit-scrollbar-track {
    background: var(--bg-color);
}

.content-area::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 4px;
}

.content-area::-webkit-scrollbar-thumb:hover {
    background: var(--highlight-color);
}

.reply-count {
    font-size: 0.8rem;
    color: var(--quote-color);
    margin-left: 10px;
}

/* レスポンシブ対応 */
@media (max-width: 768px) {
    .header {
        flex-direction: column;
        gap: 8px;
        padding: 10px;
    }
    
    .header h1 {
        font-size: 0.95rem;
    }
    
    .thread-title-header {
        width: 100%;
        font-size: 0.9rem;
    }
    
    .thread-title-header > div {
        overflow: hidden;
        text-overflow: ellipsis;
        white-space: nowrap;
    }
    
    .thread-url-link {
        font-size: 0.7rem;
        overflow: hidden;
        text-overflow: ellipsis;
        white-space: nowrap;
        display: block;
    }
    
    .board-title-header {
        font-size: 0.9rem;
    }
    
    .nav-controls {
        flex-wrap: wrap;
        width: 100%;
        justify-content: flex-start;
    }
    
    .nav-button {
        font-size: 0.8rem;
        padding: 4px 8px;
    }
    
    .view-toggle {
        font-size: 0.8rem;
        padding: 4px 8px;
    }
    
    .post {
        margin: 5px;
    }
    
    .post.reply-post {
        margin-left: calc(20px + var(--reply-depth, 0) * 20px);
    }
}