/* Reset & Base */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, sans-serif;
  background-color: #f5f5f7;
  color: #1d1d1f;
  min-height: 100vh;
  display: flex;
  justify-content: center;
  align-items: flex-start;
  padding: 40px 16px;
}

/* App Container */
.app {
  width: 100%;
  max-width: 480px;
  display: flex;
  flex-direction: column;
  gap: 24px;
}

/* Header */
.header {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.header__top {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.header__title {
  font-size: 32px;
  font-weight: 700;
  color: #1d1d1f;
}

/* Theme Toggle */
.theme-toggle {
  background: none;
  border: none;
  font-size: 24px;
  cursor: pointer;
  padding: 4px;
  border-radius: 8px;
  transition: background-color 0.2s;
  line-height: 1;
}

.theme-toggle:hover {
  background-color: #e8e8ed;
}

.header__date {
  font-size: 14px;
  color: #86868b;
  font-weight: 400;
}

/* Week Navigation */
.week-nav {
  display: flex;
  align-items: center;
  gap: 8px;
}

.week-nav__btn {
  background: none;
  border: none;
  font-size: 16px;
  color: #86868b;
  cursor: pointer;
  padding: 8px;
  border-radius: 8px;
  transition: background-color 0.2s;
  flex-shrink: 0;
}

.week-nav__btn:hover {
  background-color: #e8e8ed;
}

.week-nav__days {
  display: flex;
  flex: 1;
  gap: 4px;
  list-style: none;
}

.week-nav__day {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  padding: 10px 4px;
  border-radius: 12px;
  cursor: pointer;
  transition: background-color 0.2s;
}

.week-nav__day:hover {
  background-color: #e8e8ed;
}

.week-nav__day--selected {
  background-color: #1d1d1f;
  color: #ffffff;
}

.week-nav__day--selected:hover {
  background-color: #333336;
}

.week-nav__day--today {
  position: relative;
}

.week-nav__day--today::after {
  content: '';
  width: 5px;
  height: 5px;
  background-color: #ff3b30;
  border-radius: 50%;
  position: absolute;
  top: 4px;
  right: 8px;
}

.week-nav__day-name {
  font-size: 11px;
  font-weight: 500;
  color: #86868b;
}

.week-nav__day--selected .week-nav__day-name {
  color: #a1a1a6;
}

.week-nav__day-number {
  font-size: 16px;
  font-weight: 600;
}

.week-nav__day-count {
  font-size: 10px;
  font-weight: 500;
  color: #86868b;
  min-height: 14px;
}

.week-nav__day--selected .week-nav__day-count {
  color: #a1a1a6;
}

/* Todo Section */
.todo-section {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.todo-section__header {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.todo-section__count {
  font-size: 18px;
  font-weight: 600;
  color: #1d1d1f;
}

/* Todo Form */
.todo-form {
  display: flex;
  gap: 8px;
}

.todo-form__input {
  flex: 1;
  padding: 12px 16px;
  border: 1px solid #d2d2d7;
  border-radius: 12px;
  font-size: 14px;
  font-family: inherit;
  outline: none;
  transition: border-color 0.2s;
  background-color: #ffffff;
}

.todo-form__input:focus {
  border-color: #1d1d1f;
}

.todo-form__btn {
  padding: 12px 20px;
  background-color: #1d1d1f;
  color: #ffffff;
  border: none;
  border-radius: 12px;
  font-size: 14px;
  font-weight: 600;
  font-family: inherit;
  cursor: pointer;
  transition: background-color 0.2s;
  flex-shrink: 0;
}

.todo-form__btn:hover {
  background-color: #333336;
}

/* Todo List */
.todo-list {
  display: flex;
  flex-direction: column;
  gap: 8px;
  list-style: none;
}

.todo-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  background-color: #ffffff;
  border-radius: 12px;
  transition: opacity 0.2s;
}

.todo-item--done {
  opacity: 0.5;
}

.todo-item__checkbox {
  width: 22px;
  height: 22px;
  border: 2px solid #d2d2d7;
  border-radius: 50%;
  cursor: pointer;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.2s;
  background: none;
  padding: 0;
}

.todo-item__checkbox:hover {
  border-color: #1d1d1f;
}

.todo-item--done .todo-item__checkbox {
  background-color: #1d1d1f;
  border-color: #1d1d1f;
}

.todo-item--done .todo-item__checkbox::after {
  content: '✓';
  color: #ffffff;
  font-size: 12px;
  font-weight: 700;
}

.todo-item__text {
  flex: 1;
  font-size: 14px;
  font-weight: 400;
  word-break: break-word;
}

.todo-item--done .todo-item__text {
  text-decoration: line-through;
  color: #86868b;
}

.todo-item__delete {
  background: none;
  border: none;
  font-size: 18px;
  color: #d2d2d7;
  cursor: pointer;
  padding: 4px;
  line-height: 1;
  transition: color 0.2s;
}

.todo-item__delete:hover {
  color: #ff3b30;
}

/* Empty State */
.todo-list__empty {
  text-align: center;
  padding: 40px 0;
  color: #86868b;
  font-size: 14px;
}

/* Dark Mode */
body.dark {
  background-color: #1c1c1e;
  color: #f5f5f7;
}

body.dark .header__title {
  color: #f5f5f7;
}

body.dark .theme-toggle:hover {
  background-color: #3a3a3c;
}

body.dark .week-nav__btn {
  color: #a1a1a6;
}

body.dark .week-nav__btn:hover {
  background-color: #3a3a3c;
}

body.dark .week-nav__day:hover {
  background-color: #3a3a3c;
}

body.dark .week-nav__day--selected {
  background-color: #f5f5f7;
  color: #1c1c1e;
}

body.dark .week-nav__day--selected:hover {
  background-color: #e5e5e7;
}

body.dark .week-nav__day--selected .week-nav__day-name {
  color: #86868b;
}

body.dark .week-nav__day--selected .week-nav__day-count {
  color: #86868b;
}

body.dark .todo-section__count {
  color: #f5f5f7;
}

body.dark .todo-form__input {
  background-color: #2c2c2e;
  border-color: #3a3a3c;
  color: #f5f5f7;
}

body.dark .todo-form__input:focus {
  border-color: #f5f5f7;
}

body.dark .todo-form__btn {
  background-color: #f5f5f7;
  color: #1c1c1e;
}

body.dark .todo-form__btn:hover {
  background-color: #e5e5e7;
}

body.dark .todo-item {
  background-color: #2c2c2e;
}

body.dark .todo-item__checkbox {
  border-color: #48484a;
}

body.dark .todo-item__checkbox:hover {
  border-color: #f5f5f7;
}

body.dark .todo-item--done .todo-item__checkbox {
  background-color: #f5f5f7;
  border-color: #f5f5f7;
}

body.dark .todo-item--done .todo-item__checkbox::after {
  color: #1c1c1e;
}

body.dark .todo-item__text {
  color: #f5f5f7;
}

body.dark .todo-item__delete {
  color: #48484a;
}

/* Responsive */
@media (max-width: 480px) {
  body {
    padding: 24px 12px;
  }

  .header__title {
    font-size: 28px;
  }

  .week-nav__day {
    padding: 8px 2px;
  }

  .week-nav__day-number {
    font-size: 14px;
  }

  .week-nav__day-name {
    font-size: 10px;
  }
}