:root {
  --bg: #eef2ff;
  --surface: #ffffff;
  --surface-alt: #f8fafc;
  --text: #0f172a;
  --muted: #475569;
  --accent: #6366f1;
  --accent-strong: #4338ca;
  --danger: #b91c1c;
  --success: #0f766e;
  --expired: #dc2626;
  --completed: #047857;
  --border: #e2e8f0;
  --shadow: rgba(15, 23, 42, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  font-family: Inter, system-ui, sans-serif;
  background: radial-gradient(circle at top, #eef2ff 0%, #dbeafe 35%, #f8fafc 100%);
  color: var(--text);
  display: flex;
  justify-content: center;
  padding: 1.25rem;
}

.app-shell {
  position: relative;
  width: min(100%, 760px);
  background: var(--surface);
  border: 1px solid rgba(99, 102, 241, 0.16);
  border-radius: 30px;
  box-shadow: 0 24px 80px var(--shadow);
  padding: 1.75rem;
}

header {
  margin-bottom: 1.5rem;
}

header h1 {
  margin: 0;
  font-size: clamp(2rem, 5vw, 2.7rem);
  letter-spacing: -0.04em;
}

header p {
  margin: 0.8rem 0 0;
  color: var(--muted);
  line-height: 1.7;
}

.todo-form {
  display: grid;
  gap: 0.95rem;
  margin-bottom: 1.6rem;
  padding: 1.15rem;
  border-radius: 24px;
  background: var(--surface-alt);
  border: 1px solid rgba(148, 163, 184, 0.16);
}

.form-row {
  display: grid;
  grid-template-columns: 1.8fr 1fr;
  gap: 0.8rem;
}

.import-row {
  display: grid;
  gap: 0.75rem;
  margin-bottom: 1rem;
}

.import-row.hidden {
  display: none;
}

.import-toggle-button {
  position: absolute;
  top: 1rem;
  right: 1rem;
  width: 2.5rem;
  height: 2.5rem;
  border: none;
  border-radius: 999px;
  background: rgba(99, 102, 241, 0.12);
  color: var(--text);
  font-size: 1.15rem;
  cursor: pointer;
  display: grid;
  place-items: center;
  transition: transform 0.2s ease, background 0.2s ease;
}

.import-toggle-button:hover,
.import-toggle-button:focus-visible {
  background: rgba(99, 102, 241, 0.18);
  transform: translateY(-1px);
}

.file-input-row {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

#task-file-input {
  flex: 1;
  padding: 0.95rem 1rem;
  border: 1px solid var(--border);
  border-radius: 18px;
  background: #ffffff;
  color: var(--text);
}

#load-file-button {
  padding: 1rem 1.3rem;
  border: none;
  border-radius: 20px;
  background: linear-gradient(135deg, var(--accent), #534cce);
  color: white;
  font-weight: 700;
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

#load-file-button:hover {
  transform: translateY(-1px);
  box-shadow: 0 20px 35px rgba(99, 102, 241, 0.24);
}

#task-input,
#due-date-input {
  width: 100%;
  padding: 1rem 1.1rem;
  border: 1px solid var(--border);
  border-radius: 18px;
  font-size: 1rem;
  background: #ffffff;
  color: var(--text);
}

#task-input::placeholder {
  color: #94a3b8;
}

.todo-form button {
  width: 100%;
  padding: 1rem 1.3rem;
  border: none;
  border-radius: 20px;
  background: linear-gradient(135deg, var(--accent), #534cce);
  color: white;
  font-weight: 700;
  letter-spacing: 0.01em;
  cursor: pointer;
  box-shadow: 0 16px 30px rgba(99, 102, 241, 0.18);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.todo-form button:hover {
  transform: translateY(-1px);
  box-shadow: 0 20px 35px rgba(99, 102, 241, 0.24);
}

.tasks-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.task-sections {
  display: inline-flex;
  gap: 0.5rem;
  border: 1px solid rgba(148, 163, 184, 0.16);
  border-radius: 999px;
  padding: 0.25rem;
  background: var(--surface-alt);
}

.section-tab {
  border: none;
  background: transparent;
  color: var(--muted);
  padding: 0.75rem 1rem;
  border-radius: 999px;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.2s ease, color 0.2s ease;
}

.section-tab.active {
  background: linear-gradient(135deg, var(--accent), #4f46e5);
  color: white;
}

.section-tab:focus-visible {
  outline: 2px solid rgba(92, 95, 241, 0.35);
  outline-offset: 2px;
}

.tasks-container {
  max-height: 400px;
  overflow-y: auto;
}

.task-item {
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.2rem;
  border: 1px solid var(--border);
  border-radius: 22px;
  margin-bottom: 0.5rem;
  background: #ffffff;
  transition: border-color 0.2s ease, background 0.2s ease;
}

.task-details {
  display: grid;
  gap: 0.35rem;
  min-width: 0;
}

.task-item.completed {
  border-color: rgba(16, 185, 129, 0.25);
  background: #ecfdf5;
}

.task-item.expired {
  border-color: rgba(204, 28, 28, 0.22);
  background: #fef2f2;
}

.task-item.completed .task-label {
  color: var(--completed);
  text-decoration: line-through;
}

.task-item.due-today .task-label {
  animation: blink 1s infinite;
}

@keyframes blink {
  0%, 50% { opacity: 1; }
  51%, 100% { opacity: 0.3; }
}

.task-label {
  font-size: 1rem;
  margin: 0;
}

.task-meta {
  color: var(--muted);
  font-size: 0.92rem;
}

.task-item.expired .task-meta {
  color: var(--expired);
  font-weight: 600;
}

.task-item.completed .task-meta {
  color: #166534;
}

.task-actions {
  display: flex;
  gap: 0.55rem;
}

.task-actions button {
  border: none;
  background: rgba(148, 163, 184, 0.12);
  font-size: 0.95rem;
  cursor: pointer;
  color: var(--text);
  padding: 0.7rem 0.85rem;
  border-radius: 14px;
  transition: background 0.2s ease, transform 0.2s ease;
}

.task-actions button:hover {
  transform: translateY(-1px);
  background: rgba(148, 163, 184, 0.2);
}

.task-actions button.delete {
  color: var(--danger);
}

.task-actions button.save {
  color: var(--success);
}

.edit-input {
  width: 100%;
  border: 1px solid #cbd5e1;
  border-radius: 16px;
  padding: 0.95rem 1rem;
  font-size: 1rem;
}

@media (max-width: 680px) {
  .form-row {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 560px) {
  body {
    padding: 0.9rem;
  }

  .app-shell {
    padding: 1.25rem;
    border-radius: 24px;
  }

  .task-item {
    grid-template-columns: 1fr;
    gap: 0.85rem;
  }

  .task-actions {
    justify-content: flex-end;
  }
}