<div class="kb-board" id="kbBoard">
  <div class="kb-column" data-status="todo">
    <div class="kb-col-header">
      <span class="kb-col-title">To Do</span>
      <span class="kb-col-count" id="kbCountTodo">0</span>
    </div>
    <div class="kb-col-body" data-status="todo"></div>
  </div>
  <div class="kb-column" data-status="progress">
    <div class="kb-col-header">
      <span class="kb-col-title">In Progress</span>
      <span class="kb-col-count" id="kbCountProgress">0</span>
    </div>
    <div class="kb-col-body" data-status="progress"></div>
  </div>
  <div class="kb-column" data-status="done">
    <div class="kb-col-header">
      <span class="kb-col-title">Done</span>
      <span class="kb-col-count" id="kbCountDone">0</span>
    </div>
    <div class="kb-col-body" data-status="done"></div>
  </div>
</div>

* { box-sizing: border-box; margin: 0; padding: 0; }
body { font-family: system-ui, -apple-system, sans-serif; background: #f1f5f9; min-height: 100vh; padding: 24px; }

.kb-board { display: grid; grid-template-columns: repeat(3, minmax(220px, 1fr)); gap: 16px; max-width: 900px; margin: 0 auto; }

.kb-column {
  background: #eef1f6; border-radius: 14px; padding: 12px;
  display: flex; flex-direction: column; min-height: 320px;
  transition: background 0.15s;
}
.kb-column.kb-drag-over { background: #dbeafe; }

.kb-col-header { display: flex; align-items: center; justify-content: space-between; padding: 4px 6px 12px; }
.kb-col-title { font-size: 13px; font-weight: 800; color: #1e293b; text-transform: uppercase; letter-spacing: 0.04em; }
.kb-col-count { font-size: 11px; font-weight: 700; background: #fff; color: #64748b; padding: 2px 8px; border-radius: 999px; }

.kb-col-body { flex: 1; display: flex; flex-direction: column; gap: 8px; min-height: 60px; }

.kb-card {
  background: #fff; border-radius: 10px; padding: 12px 14px; cursor: grab;
  box-shadow: 0 1px 2px rgba(15,23,42,0.06); border-left: 3px solid #6366f1;
  font-size: 13px; color: #334155; font-weight: 600;
  transition: opacity 0.15s, transform 0.1s;
}
.kb-card:active { cursor: grabbing; }
.kb-card.kb-dragging { opacity: 0.4; transform: scale(0.98); }
.kb-card-tag { display: inline-block; margin-top: 8px; font-size: 10px; font-weight: 700; color: #6366f1; background: #eef2ff; padding: 2px 7px; border-radius: 6px; }

const columns = document.querySelectorAll('.kb-col-body');
const board = document.getElementById('kbBoard');

const TASKS = [
  { id: 't1', text: 'Design onboarding flow wireframes', tag: 'Design', status: 'todo' },
  { id: 't2', text: 'Write API docs for billing endpoints', tag: 'Docs', status: 'todo' },
  { id: 't3', text: 'Fix flaky checkout test', tag: 'Bug', status: 'progress' },
  { id: 't4', text: 'Implement dark mode toggle', tag: 'Feature', status: 'progress' },
  { id: 't5', text: 'Set up staging environment', tag: 'DevOps', status: 'done' },
  { id: 't6', text: 'Ship Q3 changelog email', tag: 'Marketing', status: 'done' },
  { id: 't7', text: 'Review pull request #482', tag: 'Review', status: 'todo' },
];

function createCard(task) {
  const card = document.createElement('div');
  card.className = 'kb-card';
  card.draggable = true;
  card.dataset.id = task.id;
  card.innerHTML = task.text + '<br><span class="kb-card-tag">' + task.tag + '</span>';

  card.addEventListener('dragstart', (e) => {
    e.dataTransfer.setData('text/plain', task.id);
    card.classList.add('kb-dragging');
  });
  card.addEventListener('dragend', () => {
    card.classList.remove('kb-dragging');
  });

  return card;
}

function updateCounts() {
  document.getElementById('kbCountTodo').textContent = document.querySelector('.kb-col-body[data-status="todo"]').children.length;
  document.getElementById('kbCountProgress').textContent = document.querySelector('.kb-col-body[data-status="progress"]').children.length;
  document.getElementById('kbCountDone').textContent = document.querySelector('.kb-col-body[data-status="done"]').children.length;
}

function renderBoard() {
  columns.forEach((col) => { col.innerHTML = ''; });
  TASKS.forEach((task) => {
    const col = document.querySelector('.kb-col-body[data-status="' + task.status + '"]');
    if (col) col.appendChild(createCard(task));
  });
  updateCounts();
}

columns.forEach((col) => {
  const columnEl = col.closest('.kb-column');

  col.addEventListener('dragover', (e) => {
    e.preventDefault();
    columnEl.classList.add('kb-drag-over');
  });

  col.addEventListener('dragleave', () => {
    columnEl.classList.remove('kb-drag-over');
  });

  col.addEventListener('drop', (e) => {
    e.preventDefault();
    columnEl.classList.remove('kb-drag-over');
    const id = e.dataTransfer.getData('text/plain');
    const task = TASKS.find((t) => t.id === id);
    if (!task) return;
    task.status = col.dataset.status;
    renderBoard();
  });
});

renderBoard();