h1 {
  width: min(600px, calc(100% - 24px));
  margin: 20px auto 10px;
  text-align: center;
}

.center {
  text-align: center;
}

body {
    font-family: sans-serif;
    background-color: #ffffff;
  }

.card {
  width: min(600px, calc(100% - 24px));
  box-sizing: border-box;
  margin: 40px auto;
  padding: 30px;
  background-color: #f7f7f8;
  border-radius: 12px;
  min-height: 160px;
  text-align: center;
  position: relative; /* ←下の.card{position:relative}と重複するので、こっちにまとめる */

  display: flex;              /* 追加 */
  justify-content: center;    /* 追加：横中央 */
  align-items: center;        /* 追加：縦中央 */
}


.progress{
  text-align: center;
}
  



.back { 
  display: none;
  margin-top: 4px;
}

.card.show-answer .front {
  display: none;
}

.card.show-answer .back {
  display: block;
}

.card.show-answer .note { display: block; }

/* 左右ナビボタン */
.nav-btn{
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  border: none;
  background: rgba(0,0,0,0.06);
  font-size: 34px;
  line-height: 1;
  padding: 6px 12px;
  border-radius: 10px;
  cursor: pointer;

  /* ちょい控えめに */
  opacity: 0.5;
}

.nav-btn:hover{
  opacity: 1;
}

.nav-left{ left: 12px; }
.nav-right{ right: 12px; }

.front,
.back {
  font-size: 28px;
}

.front {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
}

.inline-speak {
  border: none;
  background: transparent;
  font-size: 20px;
  cursor: pointer;
}
.note {
  display: none;
  margin-top: 10px;
  text-align: left;
  font-size: 16px;
  line-height: 1.5;
}

.note ul{
  margin: 0;
  padding-left: 20px;
}

.content {
  width: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;

  padding: 14px 60px;      /* ←上下14px、左右60px（矢印の逃げ） */
  box-sizing: border-box;
}

@media (max-width: 480px){
  .content {
    padding: 14px 20px;
  }
}
body {
  overflow-x: hidden;
}