:root {
    --primary-color: #4a90e2;
    --success-color: #2ecc71;
    --bg-color: #f5f7fa;
    --card-bg: #ffffff;
    --text-color: #333;
    --border-radius: 12px;
}

body {
    font-family: 'Pretendard', -apple-system, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 20px;
}

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

h1 { color: var(--primary-color); }
#cycle-display { font-weight: bold; font-size: 1.1rem; color: #555; }

.container {
    display: flex;
    gap: 30px;
    max-width: 1200px;
    margin: 0 auto;
    align-items: flex-start;
}

/* 패널 공통 스타일 */
.todo-panel, .tree-panel {
    background: var(--card-bg);
    padding: 20px;
    border-radius: var(--border-radius);
    box-shadow: 0 4px 15px rgba(0,0,0,0.05);
    min-height: 500px;
}

.todo-panel { flex: 1; }
.tree-panel { flex: 1.5; }

h2 {
    margin-top: 0;
    padding-bottom: 10px;
    border-bottom: 2px solid #f0f0f0;
    font-size: 1.25rem;
}

/* 투두 리스트 아이템 */
.todo-item {
    display: flex;
    align-items: center;
    padding: 15px;
    border-bottom: 1px solid #f0f0f0;
    gap: 12px;
}

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

.todo-item input[type="checkbox"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
}

.todo-item span {
    line-height: 1.4;
}

.todo-item.completed span {
    text-decoration: line-through;
    color: #999;
}

/* 아코디언 스타일 */
.accordion-item {
    margin-bottom: 10px;
    border: 1px solid #eee;
    border-radius: 8px;
    overflow: hidden;
}

.accordion-header {
    background: #fcfcfc;
    padding: 15px;
    cursor: pointer;
    font-weight: bold;
    display: flex;
    justify-content: space-between;
}

.accordion-header:hover { background: #f0f4f8; }

.accordion-content {
    display: none;
    padding: 10px;
    background: #fff;
}

.accordion-content.active { display: block; }

/* 소단원 행 */
.sub-chapter {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px;
    border-bottom: 1px solid #f9f9f9;
}

.sub-chapter:last-child { border-bottom: none; }

.status-badge {
    font-size: 0.8rem;
    padding: 3px 8px;
    border-radius: 20px;
    background: #eee;
    margin-right: 10px;
}

.status-badge.ongoing { background: #e3f2fd; color: #1976d2; }
.status-badge.done { background: #e8f5e9; color: #2e7d32; }

button {
    padding: 6px 12px;
    border-radius: 6px;
    border: none;
    cursor: pointer;
    background: var(--primary-color);
    color: white;
    transition: background 0.3s;
}

button:hover { background: #357abd; }
button:disabled { background: #ccc; cursor: default; }

/* 모달 */
.modal {
    position: fixed;
    top: 0; left: 0; width: 100%; height: 100%;
    background: rgba(0,0,0,0.6);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal.hidden { display: none; }

.modal-content {
    background: white;
    padding: 40px;
    border-radius: 20px;
    text-align: center;
    box-shadow: 0 10px 30px rgba(0,0,0,0.2);
    max-width: 400px;
}

.confetti { font-size: 4rem; display: block; margin-bottom: 20px; }

@media (max-width: 900px) {
    .container { flex-direction: column; }
    .todo-panel, .tree-panel { width: 100%; }
}