* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --color-bg: #f0f2f5;
  --color-surface: #ffffff;
  --color-border: #e2e5ea;
  --color-text: #1a1d23;
  --color-text-secondary: #6b7280;
  --color-primary: #4f46e5;
  --color-primary-hover: #4338ca;
  --color-danger: #ef4444;
  --color-danger-hover: #dc2626;
  --color-backlog: #8b5cf6;
  --color-todo: #f59e0b;
  --color-progress: #3b82f6;
  --color-done: #10b981;
  --color-priority-low: #6ee7b7;
  --color-priority-medium: #fcd34d;
  --color-priority-high: #fca5a5;
  --radius: 12px;
  --radius-sm: 8px;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.08), 0 2px 4px -2px rgba(0,0,0,0.05);
  --shadow-lg: 0 10px 25px -5px rgba(0,0,0,0.12), 0 4px 10px -6px rgba(0,0,0,0.06);
  --transition: 200ms ease;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  line-height: 1.5;
}

.header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 32px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 10;
}

.logo {
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.3px;
}

.header-actions {
  display: flex;
  gap: 8px;
}

.btn {
  padding: 8px 16px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition);
  display: inline-flex;
  align-items: center;
  gap: 6px;
}

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

.btn-ghost {
  background: transparent;
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border);
}
.btn-ghost:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

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

.board {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  padding: 24px 32px;
  min-height: calc(100vh - 65px);
  align-items: start;
}

.column {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 16px;
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  min-height: 300px;
}

.column-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--color-border);
}

.column-dot {
  width: 10px;
  height: 10px;
  border-radius: 50%;
  flex-shrink: 0;
}

.dot-backlog { background: var(--color-backlog); }
.dot-todo { background: var(--color-todo); }
.dot-progress { background: var(--color-progress); }
.dot-done { background: var(--color-done); }

.column-title {
  font-size: 14px;
  font-weight: 600;
  color: var(--color-text);
  flex: 1;
}

.column-count {
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-secondary);
  background: var(--color-bg);
  padding: 2px 8px;
  border-radius: 12px;
}

.task-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  flex: 1;
  min-height: 60px;
}

.task-list.drag-over {
  background: rgba(79, 70, 229, 0.05);
  border-radius: var(--radius-sm);
  outline: 2px dashed var(--color-primary);
  outline-offset: -1px;
}

.task-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  padding: 12px;
  cursor: grab;
  transition: all var(--transition);
  box-shadow: var(--shadow-sm);
  position: relative;
}

.task-card:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--color-primary);
}

.task-card:active {
  cursor: grabbing;
}

.task-card.dragging {
  opacity: 0.5;
  transform: scale(0.98);
}

.task-card-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 8px;
  margin-bottom: 6px;
}

.task-card-title {
  font-size: 14px;
  font-weight: 600;
  word-break: break-word;
  flex: 1;
}

.task-card-desc {
  font-size: 12px;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.task-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.priority-badge {
  font-size: 11px;
  font-weight: 600;
  padding: 2px 8px;
  border-radius: 4px;
  text-transform: uppercase;
  letter-spacing: 0.3px;
}

.priority-low {
  background: #d1fae5;
  color: #065f46;
}

.priority-medium {
  background: #fef3c7;
  color: #92400e;
}

.priority-high {
  background: #fee2e2;
  color: #991b1b;
}

.task-card-actions {
  display: flex;
  gap: 4px;
}

.task-card-actions button {
  width: 24px;
  height: 24px;
  border: none;
  background: transparent;
  color: var(--color-text-secondary);
  border-radius: 4px;
  cursor: pointer;
  font-size: 13px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition);
}

.task-card-actions button:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

.task-card-actions button.delete-btn:hover {
  background: #fee2e2;
  color: var(--color-danger);
}

.empty-state {
  text-align: center;
  padding: 32px 16px;
  color: var(--color-text-secondary);
  font-size: 13px;
  border: 2px dashed var(--color-border);
  border-radius: var(--radius-sm);
}

.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 100;
  backdrop-filter: blur(4px);
}

.modal {
  background: var(--color-surface);
  border-radius: var(--radius);
  padding: 24px;
  width: 90%;
  max-width: 460px;
  box-shadow: var(--shadow-lg);
  animation: modalIn 200ms ease;
}

@keyframes modalIn {
  from { opacity: 0; transform: translateY(-8px) scale(0.97); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}

.modal h3 {
  font-size: 18px;
  margin-bottom: 20px;
}

.form-group {
  margin-bottom: 16px;
}

.form-group label {
  display: block;
  font-size: 13px;
  font-weight: 500;
  color: var(--color-text-secondary);
  margin-bottom: 6px;
}

.form-group input,
.form-group textarea,
.form-group select {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-family: inherit;
  transition: border-color var(--transition);
  background: var(--color-surface);
  color: var(--color-text);
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.modal-actions {
  display: flex;
  justify-content: flex-end;
  gap: 8px;
  margin-top: 20px;
}

.hidden {
  display: none !important;
}

@media (max-width: 1024px) {
  .board {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 640px) {
  .board {
    grid-template-columns: 1fr;
    padding: 16px;
  }
  .header {
    padding: 12px 16px;
  }
  .logo {
    font-size: 16px;
  }
}