/* --- 課程title --- */
.assignment-header h1 {
    color: #343a40; 
}

/* --- 手風琴 --- */
.accordion-button {
    font-size: 1.1rem;
    font-weight: 500;
    transition: background-color 0.2s ease-in-out;
}

/* 手風琴按鈕 展開時樣式 */
.accordion-button:not(.collapsed) {
    color: #ffffff;
    background-color: var(--bs-primary); 
}

.accordion-button:not(.collapsed)::after {
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='%23ffffff'%3e%3cpath fill-rule='evenodd' d='M1.646 4.646a.5.5 0 0 1 .708 0L8 10.293l5.646-5.647a.5.5 0 0 1 .708.708l-6 6a.5.5 0 0 1-.708 0l-6-6a.5.5 0 0 1 0-.708z'/%3e%3c/svg%3e");
}

/* 滑鼠懸停在按鈕上時的樣式 */
.accordion-button:hover {
    background-color: #f0f2f5;
}

.accordion-button:focus {
    box-shadow: 0 0 0 0.25rem rgba(13, 110, 253, 0.25); /* 點下時的外框光暈 */
}

/* --- 手風琴內容 （列表） --- */
.accordion-body .list-group-item {
    border: none; 
    padding-left: 0;
    padding-right: 0;
}

.accordion-body .list-group-item a {
    color: #212529;
    font-weight: 500;
}

.accordion-body .list-group-item a:hover {
    color: var(--bs-primary);
    text-decoration: underline !important;
}


/* --- 右側邊欄 資訊卡片們 --- */
.card.sticky-top {
    border-radius: .5rem;
    border: 1px solid #dee2e6;
}

.card.sticky-top .card-header {
    font-weight: 700;
    background-color: #f8f9fa;
}

/* 深色模式：course 頁面側欄與手風琴覆寫 */
.dark-mode .card.sticky-top {
    background-color: var(--surface-color) !important;
    border-color: var(--border-color) !important;
}
.dark-mode .card.sticky-top .card-header {
    background-color: transparent !important;
    color: var(--text-color) !important;
}
.dark-mode .accordion-body .list-group-item a {
    color: var(--text-color) !important;
}

/* 強制覆寫手風琴展開內容與按鈕，在深色模式下不要顯示白色背景 */
.dark-mode .accordion .accordion-body,
.dark-mode .accordion .accordion-item,
.dark-mode .accordion .accordion-collapse,
.dark-mode .accordion .accordion-body .list-group-item {
    background-color: var(--surface-color) !important;
    color: var(--text-color) !important;
    border-color: var(--border-color) !important;
}

/* 未展開（.collapsed）與展開按鈕皆為白色文字，箭頭也強制為白色 */
.dark-mode .accordion-button,
.dark-mode .accordion-button.collapsed {
    color: #ffffff !important;
}
.dark-mode .accordion-button::after {
    background-image: url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 16 16' fill='%23ffffff'%3e%3cpath fill-rule='evenodd' d='M1.646 4.646a.5.5 0 0 1 .708 0L8 10.293l5.646-5.647a.5.5 0 0 1 .708.708l-6 6a.5.5 0 0 1-.708 0l-6-6a.5.5 0 0 1 0-.708z'/%3e%3c/svg%3e");
}