在 CSS-Grid 中创建叠加

Question

我正在尝试在 CSS3 网格中创建一个覆盖层，但我似乎不知道如何实现它。我在网上搜索过但没有找到任何帮助。我想实现如下所示的目标：

body {
  margin: 0;
  padding: 0;
}

.wrapper {
		display: grid;
		grid-template-rows: 1f;
    width: 100vw;
    height: 100vh; 
    grid-template-areas:
      "a"
      "b"
      "c";
	}

.box {
  background-color: #444;
  color: #fff;
}

.a {
  grid-area: a;
}

.b {
  grid-area: b;
}

.c {
  grid-area: c;
}

<div class="wrapper">
  <div class="box a">A</div>
  <div class="box b">B</div>
  <div class="box c">C</div>
</div>

这里是 codepen 的链接：https://codepen.io/anon/pen/PROVeY

编辑：

如何在 CSS3 网格布局中将 div 放置在左侧和右侧覆盖层上，以对抗其后面较大的 div

 body {
      margin: 0;
      padding: 0;
    }

    .wrapper {
            display: grid;
            grid-template-rows: 1f;
        width: 100vw;
        height: 100vh; 
        grid-template-areas:
          "a"
          "b"
          "c";
        }

    .box {
      background-color: #444;
      color: #fff;
    }

    .a {
      grid-area: a;
    }

    .b {
      grid-area: b;
    }

    .c {
      grid-area: c;
    }
    .D {
      grid-area: D;
    }


    <div class="wrapper">
      <div class="box a">A</div>
      <div class="box b">B</div>
      <div class="box c">C</div>
      <div class="box D">C</div>
    </div>

Answer 1

像这样：

网格模板区域并不是这里最有用的东西。最好独立定义列/行，然后分别将元素分配给它们。然后根据需要对齐它们。

body {
    margin: 0;
    padding: 0;
}

.wrapper {
  margin:auto;
  width:90vw;
    display: grid;
    height: 100vh; 
  grid-template-columns:1fr; /* only one column */
  grid-template-rows:1fr auto; /* 2 rows */
    }
.a,
.b {
  grid-column:1; /* first-column */
  grid-row:1; /* first row */
}



.b {
  width:3em;
  height:3em;
  align-self: end; /* bottom of column */
  justify-self: end; /* right of row */
  margin:1em;
}

.box {
  border:1px solid green;
}

<div class="wrapper">
  <div class="box a">A</div>
  <div class="box b">B</div>
  <div class="box c">C</div>
</div>

Answer 2

更新回答您更新的问题：

尝试下面的代码片段：

body {
    margin: 0;
    padding: 0;
}

.wrapper {
  margin:auto;
  width:90vw;
    display: grid;
    height: 100vh; 
  grid-template-columns:1fr; /* only one column */
  grid-template-rows:1fr auto; /* 2 rows */
    }
.a,
.b,.c {
  grid-column:1; /* first-column */
  grid-row:1; /* first row */
}

.c {
  width:3em;
  height:3em;
  align-self: end; /* bottom of column */
  justify-self: end; /* right of row */
  margin:1em;
}

.b {
  width:9em;
  height:3em;
  align-self: end; /* bottom of column */
  justify-self: start; /* left of row */
  margin:0.5em;
 
}

.box {
  border:1px solid green;
}

<div class="wrapper">
  <div class="box a">A</div>
  <div class="box b">B</div>
  <div class="box c">C</div>
  <div class="box d">D</div>
</div>

Answer 3

I know this is an old question, but I think css-grid is your best friend  here: 
<div class="wrapper">
  <div class="box a">A</div>
  <div class="box b">B</div>
  <div class="box c">C</div>
  <div class="box d">D</div>
</div>

.wrapper {
  display: grid;
  grid-template-columns: 2fr 4fr 1fr; /* 3 columns */
  grid-template-rows: 350px 40px 40px; /* 3 rows */
}
.a {
  background: pink;
  grid-row: 1 / 3;
  grid-column: 1 / 4;
 }

 .b {
   background: teal;
   grid-row: 2 / 3;
   grid-column: 1 / 2;
 }

 .c {
   background: yellow;
   grid-row: 2 / 3;
   grid-column: 3 / 4;
 }

 .d {
   background: orange;
   grid-row: 3 / 4;
   grid-column: 1 / 4;
 }