* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Arial', sans-serif;
}

:root {
    /* 亮色主题变量 */
    --bg-color: #f5f5f5;
    --container-bg: white;
    --text-color: #2c3e50;
    --title-color: #e74c3c;
    --secondary-text: #7f8c8d;
    --panel-bg: #f9f9f9;
    --btn-primary-bg: #3498db;
    --btn-primary-hover: #2980b9;
    --btn-primary-text: white;
    --btn-secondary-bg: #ecf0f1;
    --btn-secondary-text: #7f8c8d;
    --btn-secondary-hover: #d5dbdb;
    --btn-active-bg: #e74c3c;
    --btn-active-text: white;
    --add-btn-bg: #2ecc71;
    --add-btn-hover: #27ae60;
    --border-color: #ddd;
    --task-border: #eee;
    --complete-color: #2ecc71;
    --delete-color: #e74c3c;
    --box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
    --tab-active-border: #e74c3c;
}

.dark-theme {
    /* 暗色主题变量 */
    --bg-color: #2c3e50;
    --container-bg: #34495e;
    --text-color: #ecf0f1;
    --title-color: #e74c3c;
    --secondary-text: #bdc3c7;
    --panel-bg: #2c3e50;
    --btn-primary-bg: #3498db;
    --btn-primary-hover: #2980b9;
    --btn-primary-text: white;
    --btn-secondary-bg: #7f8c8d;
    --btn-secondary-text: #ecf0f1;
    --btn-secondary-hover: #95a5a6;
    --btn-active-bg: #e74c3c;
    --btn-active-text: white;
    --add-btn-bg: #2ecc71;
    --add-btn-hover: #27ae60;
    --border-color: #7f8c8d;
    --task-border: #7f8c8d;
    --complete-color: #2ecc71;
    --delete-color: #e74c3c;
    --box-shadow: 0 0 20px rgba(0, 0, 0, 0.3);
    --tab-active-border: #e74c3c;
}

body {
    background-color: var(--bg-color);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    color: var(--text-color);
    transition: background-color 0.3s ease;
}

.container {
    background-color: var(--container-bg);
    border-radius: 10px;
    box-shadow: var(--box-shadow);
    width: 90%;
    max-width: 1000px;
    padding: 20px;
    transition: background-color 0.3s ease, box-shadow 0.3s ease;
}

header {
    text-align: center;
    margin-bottom: 20px;
    position: relative;
}

h1 {
    color: var(--title-color);
    margin-bottom: 10px;
}

.theme-toggle-btn {
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: var(--btn-primary-bg);
    color: var(--btn-primary-text);
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
    z-index: 1000;
    transition: background-color 0.3s;
}

.theme-toggle-btn:hover {
    background-color: var(--btn-primary-hover);
}

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

.main-content {
    display: flex;
    gap: 20px;
    flex-wrap: wrap;
}

.timer-section {
    flex: 1;
    min-width: 300px;
}

.tasks-section {
    flex: 1;
    min-width: 300px;
}

.timer-container {
    background-color: var(--panel-bg);
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 20px;
    text-align: center;
    transition: background-color 0.3s ease;
}

.timer-display {
    margin-bottom: 15px;
}

#time-left {
    font-size: 3rem;
    font-weight: bold;
    color: var(--text-color);
}

#mode-label {
    font-size: 1rem;
    color: var(--secondary-text);
    margin-top: 5px;
}

.timer-controls {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-bottom: 15px;
}

.btn {
    background-color: var(--btn-primary-bg);
    color: var(--btn-primary-text);
    border: none;
    border-radius: 4px;
    padding: 8px 16px;
    cursor: pointer;
    font-size: 1rem;
    transition: background-color 0.3s;
}

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

.mode-buttons {
    display: flex;
    justify-content: center;
    gap: 10px;
}

.mode-btn {
    background-color: var(--btn-secondary-bg);
    color: var(--btn-secondary-text);
    border: none;
    border-radius: 4px;
    padding: 6px 12px;
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.3s;
}

.mode-btn:hover {
    background-color: var(--btn-secondary-hover);
}

.mode-btn.active {
    background-color: var(--btn-active-bg);
    color: var(--btn-active-text);
}

.settings-container {
    background-color: var(--panel-bg);
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 20px;
    transition: background-color 0.3s ease;
}

.settings-toggle {
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    margin-bottom: 10px;
}

.settings-toggle svg {
    transition: transform 0.3s;
}

.settings-toggle.open svg {
    transform: rotate(180deg);
}

.settings-content {
    display: none;
}

.settings-content.open {
    display: block;
}

.tasks-container {
    background-color: var(--panel-bg);
    border-radius: 8px;
    padding: 20px;
    transition: background-color 0.3s ease;
}

.tasks-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 15px;
}

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

.tasks-actions {
    display: flex;
    gap: 10px;
}

.task-tabs {
    display: flex;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 15px;
}

.task-tab {
    padding: 8px 16px;
    cursor: pointer;
    border-bottom: 2px solid transparent;
    transition: all 0.3s;
}

.task-tab.active {
    border-bottom: 2px solid var(--tab-active-border);
    color: var(--title-color);
}

h2 {
    color: var(--text-color);
    font-size: 1.2rem;
    margin-bottom: 15px;
}

.task-input {
    display: flex;
    margin-bottom: 15px;
}

#task-input {
    flex: 1;
    padding: 8px;
    border: 1px solid var(--border-color);
    border-radius: 4px 0 0 4px;
    font-size: 0.9rem;
    background-color: var(--container-bg);
    color: var(--text-color);
}

#add-task-btn {
    background-color: var(--add-btn-bg);
    color: white;
    border: none;
    border-radius: 0 4px 4px 0;
    padding: 8px 12px;
    cursor: pointer;
    transition: background-color 0.3s;
}

#add-task-btn:hover {
    background-color: var(--add-btn-hover);
}

.task-list {
    list-style-type: none;
    max-height: 300px;
    overflow-y: auto;
}

.task-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
    border-bottom: 1px solid var(--task-border);
}

.task-item:last-child {
    border-bottom: none;
}

.task-text {
    flex: 1;
}

.completed {
    text-decoration: line-through;
    color: var(--secondary-text);
}

.task-actions {
    display: flex;
    gap: 5px;
}

.task-btn {
    background-color: transparent;
    border: none;
    cursor: pointer;
    font-size: 0.9rem;
    padding: 2px 5px;
    border-radius: 3px;
}

.complete-btn {
    color: var(--complete-color);
}

.delete-btn {
    color: var(--delete-color);
}

.task-date {
    font-size: 0.8rem;
    color: var(--secondary-text);
    margin-top: 3px;
}

.help-icon {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background-color: var(--secondary-text);
    color: var(--container-bg);
    font-size: 14px;
    margin-left: 5px;
    cursor: pointer;
}

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    z-index: 1001;
    justify-content: center;
    align-items: center;
}

.modal.open {
    display: flex;
}

.modal-content {
    background-color: var(--container-bg);
    border-radius: 8px;
    padding: 20px;
    max-width: 500px;
    width: 90%;
    position: relative;
}

.modal-close {
    position: absolute;
    top: 10px;
    right: 10px;
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--secondary-text);
}

.modal-title {
    margin-bottom: 15px;
    color: var(--title-color);
}

.modal-body {
    margin-bottom: 15px;
    
    max-height: 80vh;
    overflow-y: auto;
}

.modal-body p {
    margin-bottom: 10px;
}

.modal-body ul {
    margin-left: 20px;
    margin-bottom: 10px;
}

.modal-body li {
    margin-bottom: 5px;
}

.date-filter {
    margin-bottom: 15px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.date-filter label {
    font-size: 0.9rem;
}

.date-filter input {
    padding: 5px;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background-color: var(--container-bg);
    color: var(--text-color);
}

.no-tasks {
    text-align: center;
    color: var(--secondary-text);
    padding: 20px 0;
}

/* 底部版权信息样式 */
.footer {
    margin-top: 30px;
    padding: 15px 0;
    text-align: center;
    border-top: 1px solid var(--border-color);
    color: var(--secondary-text);
    font-size: 0.9rem;
}

.footer-content {
    max-width: 1000px;
    margin: 0 auto;
    padding: 0 20px;
}

.footer a {
    color: var(--btn-primary-bg);
    text-decoration: none;
    transition: color 0.3s;
}

.footer a:hover {
    color: var(--btn-primary-hover);
    text-decoration: underline;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .container {
        width: 95%;
        padding: 15px;
    }
    
    .main-content {
        flex-direction: column;
    }
    
    #time-left {
        font-size: 2.5rem;
    }
    
    .mode-buttons {
        flex-wrap: wrap;
    }
}