:root {
    --bg-color: #f5f8fa;
    --text-color: #14171a;
    --card-bg: #ffffff;
    --card-hover: #e1e8ed;
    --link-color: #1da1f2;
    --border-color: #ccd6dd;
    --secondary-text: #657786;
}

[data-theme="dark"] {
    --bg-color: #15202b;
    --text-color: #ffffff;
    --card-bg: #192734;
    --card-hover: #22303c;
    --link-color: #1da1f2;
    --border-color: #38444d;
    --secondary-text: #8899a6;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 0;
    transition: background-color 0.3s, color 0.3s;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 40px;
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

header h1 {
    margin: 0;
    color: var(--link-color);
    font-size: 1.5rem;
}

button {
    background-color: var(--link-color);
    color: white;
    border: none;
    padding: 8px 16px;
    border-radius: 20px;
    cursor: pointer;
    font-weight: bold;
    transition: opacity 0.2s;
}

button:hover {
    opacity: 0.9;
}

.back-btn {
    background-color: transparent;
    color: var(--link-color);
    border: 1px solid var(--link-color);
    margin-bottom: 20px;
}

main {
    flex: 1;
    width: 100%;
    max-width: 800px;
    margin: 40px auto;
    padding: 0 20px;
    box-sizing: border-box;
}

.topic-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

.topic-card {
    position: relative;
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 12px;
    padding: 20px;
    cursor: pointer;
    transition: transform 0.2s, background-color 0.2s, box-shadow 0.2s;
    box-shadow: 0 2px 5px rgba(0,0,0,0.05);
}

.topic-card:hover {
    transform: translateY(-3px);
    background-color: var(--card-hover);
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}

.topic-card h2 {
    margin-top: 0;
    font-size: 1.2rem;
    color: var(--text-color);
}

.topic-card p {
    color: var(--secondary-text);
    font-size: 0.95rem;
    line-height: 1.5;
}

.topic-card small {
    display: block;
    margin-top: 15px;
    color: var(--link-color);
    font-weight: bold;
}

.topic-header {
    margin-bottom: 30px;
    text-align: center;
}

.topic-header h2 {
    font-size: 1.8rem;
    margin-bottom: 10px;
}

.topic-header p {
    color: var(--secondary-text);
}

.tweet-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
}

.tweet-wrapper {
    position: relative;
    width: 100%;
    max-width: 550px;
    min-height: 200px; /* 防止加载时页面跳动 */
    display: flex;
    justify-content: center;
}

/* 删除按钮样式 */
.delete-btn {
    position: absolute;
    top: 10px;
    right: 10px;
    background: transparent;
    border: none;
    font-size: 1.2rem;
    cursor: pointer;
    opacity: 0.3;
    padding: 5px;
    transition: opacity 0.2s, transform 0.2s;
    z-index: 10;
}

.delete-btn:hover {
    opacity: 1;
    transform: scale(1.1);
}

.tweet-delete-btn {
    top: 0;
    right: -40px; /* 放在推文卡片外部右侧 */
}

@media (max-width: 650px) {
    .tweet-delete-btn {
        right: 0;
        top: -30px;
    }
}

footer {
    text-align: center;
    padding: 20px;
    color: var(--secondary-text);
    font-size: 0.9em;
    border-top: 1px solid var(--border-color);
    margin-top: 40px;
}