无法在手机或小屏幕上维护CSS网格结构

Question

我希望我的网站在切换到手机时保持网格结构，即在单行中具有与在桌面视图中存在时相同的列数。更清楚的是，我希望我的网站在台式机或手机上看起来一样。

我的桌面视图网站在一行中有5列，我想在移动视图上保持这一点。

任何人都可以帮助我吗？我是CSS网格结构的新手。

/* CSS Variables */
:root {
  --primary: #ddd;
  --dark: #333;
  --light: #fff;
  --shadow: 0 1px 5px rgba(104, 104, 104, 0.8);
}
html {
  box-sizing: border-box;
  font-family: Arial, Helvetica, sans-serif;
  color: var(--dark);
}
body {
  background: #ccc;
  margin: 30px 50px;
  line-height: 1.4;
}
.btn {
  background: var(--dark);
  color: var(--light);
  padding: 0.6rem 1.3rem;
  text-decoration: none;
  border: 0;
}
img {
  max-width: 100%;
}
.wrapper {
  display: grid;
  grid-gap: 20px;
}
/* Navigation */

.main-nav ul {
  display: grid;
  grid-gap: 20px;
  padding: 0;
  list-style: none;
  grid-template-columns: repeat(4, 1fr);
}
.main-nav a {
  background: var(--primary);
  display: block;
  text-decoration: none;
  padding: 0.8rem;
  text-align: center;
  color: var(--dark);
  text-transform: uppercase;
  font-size: 1.1rem;
  box-shadow: var(--shadow);
}
.main-nav a:hover {
  background: var(--dark);
  color: var(--light);
}
/* Top Container */

.top-container {
  display: grid;
  grid-gap: 20px;
  grid-template-areas: 'showcase showcase top-box-a' 'showcase showcase top-box-b';
}
/* Showcase */

.showcase {
  grid-area: showcase;
  min-height: 400px;
  background: url(https://image.ibb.co/kYJK8x/showcase.jpg);
  background-size: cover;
  background-position: center;
  padding: 3rem;
  display: flex;
  flex-direction: column;
  align-items: start;
  justify-content: center;
  box-shadow: var(--shadow);
}
.showcase h1 {
  font-size: 4rem;
  margin-bottom: 0;
  color: var(--light);
}
.showcase p {
  font-size: 1.3rem;
  margin-top: 0;
  color: var(--light);
}
/* Top Box */

.top-box {
  background: var(--primary);
  display: grid;
  align-items: center;
  justify-items: center;
  box-shadow: var(--shadow);
  padding: 1.5rem;
}
.top-box .price {
  font-size: 2.5rem;
}
.top-box-a {
  grid-area: top-box-a;
}
.top-box-b {
  grid-area: top-box-b;
}
/* Boxes */

.boxes {
  display: grid;
  grid-gap: 20px;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}
.box {
  background: var(--primary);
  text-align: center;
  padding: 1.5rem 2rem;
  box-shadow: var(--shadow);
}
/* Info */

.info {
  background: var(--primary);
  box-shadow: var(--shadow);
  display: grid;
  grid-gap: 30px;
  grid-template-columns: repeat(2, 1fr);
  padding: 3rem;
}
/* Portfolio */

.portfolio {
  display: grid;
  grid-gap: 20px;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
}
.portfolio img {
  width: 100%;
  box-shadow: var(--shadow);
}
/* Footer */

footer {
  margin-top: 2rem;
  background: var(--dark);
  color: var(--light);
  text-align: center;
  padding: 1rem;
}
/* Media Queries */

@media (max-width: 700px) {
  .top-container {
    grid-template-areas: 'showcase showcase' 'top-box-a top-box-b';
  }
  .showcase h1 {
    font-size: 2.5rem;
  }
  .main-nav ul {
    grid-template-columns: 1fr;
  }
  .info {
    grid-template-columns: 1fr;
  }
  .info .btn {
    display: block;
    text-align: center;
    margin: auto;
  }
}
@media (max-width: 500px) {
  .top-container {
    grid-template-areas: 'showcase' 'top-box-a' 'top-box-b';
  }
}

<div class="wrapper">
  <!-- Navigation -->
  <nav class="main-nav">
    <ul>
      <li>
        <a href="#">Home</a>
      </li>
      <li>
        <a href="#">About</a>
      </li>
      <li>
        <a href="#">Services</a>
      </li>
      <li>
        <a href="#">Contact</a>
      </li>
    </ul>
  </nav><!-- Top Container -->
  <section class="top-container">
    <header class="showcase">
      <h1>Your Web Presence</h1>
      <p>Lorem ipsum</p><a class="btn" href="#">Read More</a>
    </header>
    <div class="top-box top-box-a">
      <h4>GENERAL KNOWLEDGE</h4>
      <p class="price">$199/mo</p><a class="btn" href="">Buy Now</a>
    </div>
    <div class="top-box top-box-b">
      <h4>BOLLYWOOD</h4>
      <p class="price">$299/mo</p><a class="btn" href="">Buy Now</a>
    </div>
  </section><!-- Boxes Section -->
  <section class="boxes">
    <div class="box">
      <i class="fas fa-chart-pie fa-4x"></i>
      <h3>Analytics</h3>
      <p>Lorem ipsum</p>
    </div>
    <div class="box">
      <i class="fas fa-chart-pie fa-4x"></i>
      <h3>Analytics</h3>
      <p>Lorem ipsum</p>
    </div>
    <div class="box">
      <i class="fas fa-chart-pie fa-4x"></i>
      <h3>Analytics</h3>
      <p>Lorem ipsum</p>
    </div>
    <div class="box">
      <i class="fas fa-chart-pie fa-4x"></i>
      <h3>Analytics</h3>
      <p>Lorem ipsum</p>
    </div>
  </section>
</div>