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

body {
  font-family: sans-serif;
  background: #f5f5f5;
  font-size: 18px;
}

.hidden {
  display: none !important;
}

/* 登入畫面 */
#login-screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  height: 100vh;
  gap: 24px;
}

#login-screen h1 {
  font-size: 32px;
}

/* 導覽列 */
nav {
  background: #2c3e50;
  color: white;
  padding: 12px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.nav-title {
  font-size: 20px;
  font-weight: bold;
}

.nav-links {
  display: flex;
  gap: 12px;
}

/* 頁面內容 */
.page {
  padding: 20px;
  max-width: 800px;
  margin: 0 auto;
}

/* 輸入框與按鈕 */
input {
  width: 100%;
  padding: 14px;
  margin: 8px 0;
  font-size: 18px;
  border: 1px solid #ccc;
  border-radius: 8px;
}

button {
  padding: 14px 24px;
  font-size: 18px;
  border: none;
  border-radius: 8px;
  background: #2c3e50;
  color: white;
  cursor: pointer;
  margin: 4px;
}

button:active {
  opacity: 0.8;
}

/* 購物車 */
#cart-list {
  margin: 16px 0;
}

.cart-item {
  background: white;
  padding: 12px;
  border-radius: 8px;
  margin: 8px 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

#cart-total {
  font-size: 24px;
  font-weight: bold;
  margin: 12px 0;
}

#change-display {
  font-size: 22px;
  color: #27ae60;
  margin: 8px 0;
}

/* 商品列表 */
.product-item {
  background: white;
  padding: 12px;
  border-radius: 8px;
  margin: 8px 0;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

/* 數字鍵盤 */
#numpad {
  margin: 12px 0;
}

.numpad-row {
  display: flex;
  gap: 8px;
  margin: 8px 0;
}

.numpad-btn {
  flex: 1;
  padding: 18px;
  font-size: 22px;
  background: #ecf0f1;
  color: #2c3e50;
  border-radius: 8px;
  border: 1px solid #bdc3c7;
}

.numpad-btn:active {
  background: #bdc3c7;
}

.numpad-btn[data-val="CLR"] {
  background: #e74c3c;
  color: white;
}

.numpad-btn[data-val="DEL"] {
  background: #e67e22;
  color: white;
}

/* 總計找零結帳同一排 */
.checkout-bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: white;
  padding: 12px 16px;
  border-radius: 8px;
  margin: 12px 0;
  gap: 12px;
}

#cart-total {
  font-size: 22px;
  font-weight: bold;
  white-space: nowrap;
}

#change-display {
  font-size: 20px;
  font-weight: bold;
  color: #27ae60;
  flex: 1;
  text-align: center;
}

#checkout-btn {
  white-space: nowrap;
  background: #2c3e50;
  padding: 14px 20px;
}