崩れ起点で決めるブレークポイント戦略

<section class="feature-grid">
    <article class="feature-card">料金プランの比較</article>
    <article class="feature-card">学習進捗の可視化</article>
    <article class="feature-card">質問テンプレート集</article>
    <article class="feature-card">作品ポートフォリオ</article>
</section>

.feature-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 16px;
}

.feature-card {
    padding: 16px;
    border-radius: 12px;
    background: #f0f9ff;
}

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

.page {
    padding: 16px;
}

.card-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 12px;
}

/* 768px: 2カラム化できる幅 */
@media (min-width: 768px) {
    .page {
        padding: 24px;
    }

    .card-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 16px;
    }
}

/* 1080px: 3カラム化できる幅 */
@media (min-width: 1080px) {
    .page {
        padding: 32px;
    }

    .card-grid {
        grid-template-columns: repeat(3, 1fr);
        gap: 20px;
    }
}

<form class="booking-form">
    <label>
        氏名
        <input type="text" placeholder="山田 花子">
    </label>
    <label>
        電話番号
        <input type="tel" placeholder="090-1234-5678">
    </label>
    <label>
        日付
        <input type="date">
    </label>
    <label>
        人数
        <select>
            <option>1名</option>
            <option>2名</option>
            <option>3名</option>
        </select>
    </label>
</form>

.booking-form {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 12px;
}

.booking-form input,
.booking-form select {
    width: 100%;
    padding: 10px;
}

.booking-form {
    display: grid;
    grid-template-columns: 1fr;
  gap: 16px;
  padding: 16px;
  border: 1px solid #dbe4ee;
  border-radius: 16px;
  background: linear-gradient(180deg, #ffffff 0%, #f8fbff 100%);
  box-shadow: 0 10px 30px rgba(15, 23, 42, 0.06);
}

.booking-form label {
  display: grid;
  gap: 8px;
  color: #0f172a;
  font-size: 0.95rem;
  font-weight: 700;
}

.booking-form input,
.booking-form select {
    width: 100%;
  min-height: 48px;
  padding: 0 14px;
  box-sizing: border-box;
  border: 1px solid #cbd5e1;
  border-radius: 12px;
  background: #ffffff;
  color: #334155;
  font: inherit;
}

.booking-form input:focus,
.booking-form select:focus {
  outline: none;
  border-color: #14b8a6;
  box-shadow: 0 0 0 4px rgba(20, 184, 166, 0.15);
}

@media (min-width: 760px) {
    .booking-form {
    grid-template-columns: repeat(2, minmax(0, 1fr));
        gap: 16px;
    }
}