/* --- BIẾN TOÀN CỤC CHO GIAO DIỆN --- */
:root {
    --board-bg: #f4f7fa; /* Nền của toàn bộ bảng */
    --column-bg: #e9ecef; /* Nền của cột */
    --card-bg: #ffffff; /* Nền của thẻ task */
    --card-shadow: rgba(0, 0, 0, 0.05) 0px 4px 12px;
    --card-hover-shadow: rgba(0, 0, 0, 0.1) 0px 8px 24px;
    --text-primary: #1a253c;
    --text-secondary: #6c757d;
    --border-radius: 8px;
    --gray-bg-soft: rgba(108, 117, 125, 0.1); /* Xám nhạt cho To Do */
    --gray-text: #6c757d; /* Xám cho To Do */
    --primary-bg-soft: rgba(13, 110, 253, 0.1); /* Xanh dương nhạt cho In Progress */
    --primary-text: #0d6efd; /* Xanh dương cho In Progress */
    --success-bg-soft: rgba(25, 135, 84, 0.1); /* Xanh lá nhạt cho Done */
    --success-text: #198754; /* Xanh lá cho Done */
    --danger-bg-soft: rgba(220, 53, 69, 0.1); /* Đỏ nhạt cho task quá hạn (khác Done) */
    --danger-text: #dc3545; /* Đỏ cho task quá hạn (khác Done) */
}

body {
    background-color: var(--board-bg);
}

/* --- CONTAINER CHÍNH --- */
.taskboard-header {
    margin-bottom: 2rem;
}

.taskboard-container {
    display: flex;
    gap: 20px;
    overflow-x: auto;
    padding-bottom: 20px;
}

/* --- CỘT TRẠNG THÁI --- */
.task-column {
    flex: 1 0 300px;
    min-width: 300px;
    max-width: 320px;
    background-color: var(--column-bg);
    border-radius: var(--border-radius);
    display: flex;
    flex-direction: column;
}

.column-header {
    padding: 1rem 1.2rem;
    border-bottom: 3px solid transparent;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.column-title {
    font-weight: 600;
    color: var(--text-primary);
}

.task-count-badge {
    background-color: rgba(0, 0, 0, 0.1);
    color: var(--text-primary);
    font-size: 0.8rem;
    font-weight: 600;
    padding: 4px 8px;
    border-radius: 12px;
}

/* --- DANH SÁCH TASK --- */
.task-list {
    list-style: none;
    padding: 10px;
    flex-grow: 1;
    min-height: 200px;
    transition: background-color 0.2s ease;
    position: relative;
}

.task-list-empty {
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    color: var(--text-secondary);
    font-style: italic;
    padding: 2rem;
    border: 2px dashed #ced4da;
    border-radius: var(--border-radius);
    margin: 10px;
    height: calc(100% - 20px);
    position: absolute;
    top: 0;
    left: 0;
    width: calc(100% - 20px);
}

/* --- THẺ TASK --- */
.task-card {
    background-color: var(--card-bg);
    border: 1px solid #e0e0e0;
    border-radius: var(--border-radius);
    margin-bottom: 15px;
    box-shadow: var(--card-shadow);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    cursor: grab;
    position: relative;
    z-index: 1;
}

    .task-card:hover {
        transform: translateY(-3px);
        box-shadow: var(--card-hover-shadow);
    }

    .task-card.to-do {
        background-color: var(--light-bg-soft);
        border-left: 4px solid var(--gray-text);
    }

    .task-card.in-progress {
        background-color: var(--primary-bg-soft);
        border-left: 4px solid var(--primary-text);
    }

    .task-card.done {
        background-color: var(--success-bg-soft);
        border-left: 4px solid var(--success-text);
    }

    .task-card.review {
        background-color: rgba(255, 193, 7, 0.1); /* Vàng nhạt */
        border-left: 4px solid #ffc107; /* Vàng */
    }

    .task-card.overdue:not(.done) {
        background-color: var(--danger-bg-soft);
        border-left: 4px solid var(--danger-text);
    }

.task-card-body {
    padding: 1rem;
}

.task-title {
    font-weight: 600;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.task-description {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 1rem;
}

/* --- FOOTER CỦA THẺ TASK --- */
.task-card-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-top: 1px solid #f0f0f0;
    padding: 0.75rem 1rem;
}

.due-date-badge {
    font-size: 0.8rem;
    padding: 0.3em 0.6em;
}

    .due-date-badge.overdue {
        background-color: var(--danger-text) !important;
        color: white !important;
    }

.task-actions {
    display: flex;
    align-items: center;
    gap: 5px;
    opacity: 0;
    transition: opacity 0.2s ease;
}

.task-card:hover .task-actions {
    opacity: 1;
}

.task-actions .btn {
    border-radius: 50%;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
}

/* --- TRẠNG THÁI KÉO THẢ (jQuery UI Sortable) --- */
.task-placeholder {
    background-color: rgba(0, 123, 255, 0.1);
    border: 2px dashed #0d6efd;
    border-radius: var(--border-radius);
    height: 100px;
    margin-bottom: 15px;
}

.ui-sortable-helper {
    transform: rotate(3deg);
    box-shadow: var(--card-hover-shadow) !important;
    cursor: grabbing !important;
}

/* --- RESPONSIVE CHO MOBILE --- */
@media (max-width: 768px) {
    .taskboard-container {
        flex-direction: column;
        gap: 25px;
        overflow-x: hidden;
    }

    .task-column {
        flex: 1 1 auto;
        max-width: 100%;
    }

    .taskboard-header {
        flex-direction: column;
        align-items: flex-start !important;
        gap: 1rem;
    }

    .task-actions {
        opacity: 1;
    }
}