:root {
    --primary-color: #07c160; /* WeChat Green */
    --danger-color: #fa5151;
    --text-main: #333;
    --text-sub: #888;
    --bg-color: #f7f7f7;
    --card-bg: #fff;
    --border-color: #eee;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    height: 100vh;
    overflow: hidden;
}

.app-container {
    display: flex;
    flex-direction: column;
    height: 100%;
    max-width: 600px;
    margin: 0 auto;
    background: #fff;
    position: relative;
}

/* Header */
.top-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 16px;
    background: #fff;
    border-bottom: 1px solid var(--border-color);
}

.stats {
    font-size: 18px;
    font-weight: bold;
}

.icon-btn {
    background: none;
    border: 1px solid var(--border-color);
    padding: 6px 12px;
    border-radius: 4px;
    margin-left: 8px;
    cursor: pointer;
    font-size: 14px;
}

.icon-btn.primary {
    background: var(--primary-color);
    color: #fff;
    border: none;
}

/* Search Bar */
.search-bar-container {
    padding: 10px 16px;
    background: #fff;
    border-bottom: 1px solid var(--border-color);
}

.search-input-wrapper {
    position: relative;
    display: flex;
    align-items: center;
    background: #f5f5f5;
    border-radius: 6px;
    padding: 8px 12px;
}

.search-icon {
    color: #999;
    margin-right: 8px;
    font-size: 14px;
}

#input-search {
    flex: 1;
    border: none;
    background: transparent;
    font-size: 16px;
    outline: none;
    padding: 0;
    color: var(--text-main);
}

#btn-clear-search {
    background: #ccc;
    color: #fff;
    border: none;
    border-radius: 50%;
    width: 18px;
    height: 18px;
    font-size: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    margin-left: 8px;
}

#btn-clear-search.hidden {
    display: none;
}

/* Tabs */
.tabs {
    display: flex;
    background: #fff;
    border-bottom: 1px solid var(--border-color);
    position: sticky; /* 吸顶效果 */
    top: 0;
    z-index: 10;
}

.tab {
    flex: 1;
    text-align: center;
    padding: 14px 0;
    font-size: 16px;
    color: var(--text-sub);
    cursor: pointer;
    position: relative;
}

.tab.active {
    color: var(--primary-color);
    font-weight: 500;
}

.tab.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 25%;
    width: 50%;
    height: 3px;
    background: var(--primary-color);
    border-radius: 3px 3px 0 0;
}

/* Content Area */
.content-area {
    flex: 1;
    overflow-y: auto;
    padding: 10px;
    background: var(--bg-color);
}

.student-list {
    display: none;
}

.student-list.active {
    display: block;
}

.empty-state {
    text-align: center;
    padding: 40px;
    color: var(--text-sub);
}

/* Cards */
.card {
    background: var(--card-bg);
    padding: 16px;
    margin-bottom: 10px;
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0,0,0,0.05);
    display: flex;
    justify-content: space-between;
    align-items: center;
    cursor: pointer;
    transition: transform 0.1s;
    user-select: none;
}

.card:active {
    transform: scale(0.98);
    background: #f0f0f0;
}

.card-info {
    flex: 1;
}

.card-name {
    font-size: 18px;
    font-weight: 500;
}

.card-meta {
    font-size: 12px;
    color: var(--text-sub);
    margin-top: 4px;
}

.card-action {
    font-size: 24px;
    color: var(--text-sub);
}

.card.leave-card {
    border-left: 4px solid orange;
}

.card.signed-card {
    border-left: 4px solid var(--primary-color);
    opacity: 0.8;
}

/* Floating Action Button (Removed) */
/* .floating-action { ... } */

/* Modals */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
    z-index: 100;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: opacity 0.2s;
}

.modal.hidden {
    display: none;
    opacity: 0;
    pointer-events: none;
}

/* Bottom Sheet Style */
.modal.bottom-sheet {
    align-items: flex-end;
}

.modal.bottom-sheet .modal-content {
    border-radius: 12px 12px 0 0;
    width: 100%;
    max-width: 600px; /* match container */
    margin: 0 auto;
    animation: slideUp 0.3s ease-out;
}

@keyframes slideUp {
    from { transform: translateY(100%); }
    to { transform: translateY(0); }
}

.modal-content {
    background: #fff;
    width: 90%;
    max-width: 400px;
    border-radius: 12px;
    padding: 20px;
    animation: popIn 0.2s ease-out;
}

.full-width {
    width: 100%;
    margin-top: 10px;
    text-align: center;
}

@keyframes popIn {
    from { transform: scale(0.9); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

.modal h3 {
    margin-bottom: 10px;
}

.hint {
    font-size: 12px;
    color: var(--text-sub);
    margin-bottom: 12px;
    line-height: 1.4;
}

textarea {
    width: 100%;
    height: 120px;
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    resize: none;
    font-size: 14px;
    margin-bottom: 16px;
}

.modal-actions {
    display: flex;
    justify-content: flex-end;
    gap: 12px;
}

.modal-actions button {
    padding: 8px 16px;
    border-radius: 6px;
    border: none;
    font-size: 14px;
    cursor: pointer;
}

.btn-cancel {
    background: #f0f0f0;
    color: #666;
}

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

.menu-btn {
    display: block;
    width: 100%;
    padding: 12px;
    text-align: left;
    background: none;
    border: none;
    border-bottom: 1px solid #eee;
    font-size: 16px;
    cursor: pointer;
}

.menu-btn.danger {
    color: var(--danger-color);
}

.form-group {
    margin-bottom: 15px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-size: 14px;
    color: #666;
}

.form-group input {
    width: 100%;
    padding: 8px;
    border: 1px solid #ddd;
    border-radius: 4px;
    font-size: 16px;
}