Question: How come Intellij works well with JDK 10.0.2, while netbeans won't even open a new project? I tried to work with Netbeans, but it wouldn't open. However Intellij works very well.

Answer: 
You could use `:after` pseudo element to create one square and then use `rotate` and `translate` transforms.

```css
.element {
  display: inline-block;
  background: lightgreen;
  position: relative;
  width: 200px;
  height: 200px;
  overflow: hidden;
}
.two {
  margin-left: 30px;
  width: 300px;
  height: 300px;
}

.element:after {
  content: "";
  position: absolute;
  width: 120%;
  height: 120%;
  background: #30373F;
  transform: rotate(45deg) translate(10%, -20%);
}
```

```html
<div class="element"></div>
<div class="element two"></div>
```
You can easily do this with gradient:

```css
.box {
  width:200px;
  height:200px;
  background:
    linear-gradient(red,red) right/30% 100%,
    linear-gradient(to top left,red 49.8%,transparent 50%) top left/70% 50%,
    linear-gradient(to bottom left,red 49.8%,transparent 50%) bottom left/70% 50%,
    url(https://picsum.photos/600/600?image=1069) center/cover; 
  background-repeat:no-repeat;
}
```

```html
<div class="box">
</div>
```