CSS is gaining powers with recent web evolution. And it is very clever with tricks that were long existing or that have emerged. Perhaps tricks shared here will school you with CSS tricks from the depths you were yet to explore.

Let's dive in.

1. Draw a triangle using border

   It can be an overkill to load images in cases where you need simple triangles e.g when adding an arrow pointer to a tooltip.

   Using only CSS, you can create a triangle using borders.
   
   It is quite an old trick. Ideally, on an element with zero width and height, you set borders on it. All border colors are transparent except the one that will form an arrow. To create an arrow pointing upwards, for example, the bottom border is colored while the left and right are transparent. No need to include the top border. The border width determines size of the arrow:
   

   .upwards-arrow {
       width: 0;
       height: 0;
       border-left: 20px solid transparent;
       border-right: 20px solid transparent;
   
       border-bottom: 20px solid crimson;
   }
   

   This creates an arrow pointing upwards like shown below:

   

   You can see this codepen that visualizes the concept should it be tricky to create a mental picture.

2. Interchange background of an element

   z-index property arranges how an element is stacked onto other positioned elements. At times you may set a z-index property on a child element to be lower and it ends up hiding behind the background of its parent. To prevent this, you can cause a new stacking context on the parent element to prevent child elements from going behind it. One way way to create a stacking context is to use isolation: isolate css style declaration.
   
   We can use this stacking context technique to create hover effect that interchanges a button's background. For example:
   

   button.join-now {
       cursor: pointer;
       border: none;
       outline: none;
       padding: 10px 15px;
   
       position: relative;
       background-color: #5dbea3;
       isolation: isolate; /* If ommitted, child pseudo element will be stacked behind */
   }
   
   button.join-now::before {
       content: "";
       position: absolute;
       background-color: #33b249;
       top: 0;
       left: 100%;
       right: 0;
       bottom: 0;
       transition: left 500ms ease-out;
   
       z-index: -1;
   }
   
   button.join-now:hover::before {
       left: 0;
   }
   

   The code above interchanges the background of the button when hovered. The background changes without interfering with the text on the foreground, as seen in the gif below:

   

3. Center an element

   Probably, you already know how to center an element using display: flex; and display: grid;. Yet another unpopular way to center an element on the x axis is to use text-align CSS property. This property works out of the box when centering text. To also center other elements in the DOM, a child element needs to have a display of inline. It could be inline-block or any other inline...
   

   div.parent {
       text-align: center;
   }
   
   div.child {
       display: inline-block;
   }
   

4. Pill 💊 shape button

   You can make buttons that are pill-shaped by setting the border-radius of a button to be a very high value. Certainly, the border-radius should be higher than the height of the button.
   

   button.btn {
       border-radius: 80px; /* value higher than height of the button */
       padding: 20px 30px;
       background-color: #fdd835;
       border: none;
       color: black;
       font-size: 20px;
   }
   

   result:

   

   Height of the button may increase with design changes. Hence you will often find it convenient to set border-radius with a very high value so that your css keeps working regardless if the button grows.

5. Easily add beautiful loading indicator to your website

   As it is with developers, it is often a boring task to divert your focus to creating a beautiful loading indicator for your website. This focus is better utilized building other important parts of a project that deserve attention.

   As you are reading, odds are high you also find this an annoying hurdle. That is why i took the time to take away this hurdle away from you and prepare nicely done loading indicators packaged in a library so you can "plug 'n play" from your dream project. It is a whole collection and you just need to pick the one that pulls the spark 💖 on you. Just see the simple usage of this library, with the source available on Github. Don't forget to leave a star ⭐.

6. Easy dark or light mode

   You only require a few lines of CSS to enable a dark/light mode on your website. You just need to let browsers know that your website can display correctly in system dark/light mode:
   

   html {
       color-scheme: light dark;
   }
   

   Note: color-scheme property can be set on any DOM element other than html.

   Then set variables that control background color and text color through your website, making it even more bullet proof by checking for browser support:
   

   html {
       --bg-color: #ffffff;
       --txt-color: #000000;
   }
   
   @supports (background-color: Canvas) and (color: CanvasText) {
       :root {
           --bg-color: Canvas;
           --txt-color: CanvasText;
       }
   }
   

   Note: If you don't set background-color on an element, it will inherit the browser-defined system color for the dark/light theme matched. These system colors can be different between different browsers.

   Setting background-color explicitly can be useful in combination with prefers-color-scheme to give a different shade of color different from the default that the browser sets.

   Below is the dark/light mode in action. User's preference is simulated between dark and light mode.

   

7. Truncate overflowing text with an ellipsis(...)

   This trick has been around for a while to aesthetically trim long text. But you may still have missed it.
   
   All you need is the following CSS:
   

   p.intro {
       width: 300px;
       overflow: hidden;
       text-overflow: ellipsis;
       white-space: nowrap;
   }
   

   Just implement these rules:

   • Explicit width, so bounds for clipping will ever be reached.
   • Browser wraps below long text that do not fit within an element's width. So you need to prevent that: white-space: nowrap;.
   • Content that overflows should be clipped: overflow: hidden;.
   • Pad a string with an ellipsis(...) when text is about to be clipped: text-overflow: ellipsis;.

   Result looks like this:

   

8. Truncate long text to a number of lines

   This is slightly different from the trick above. This time, text is clipped limiting content to a number of lines.
   

   p.intro {
       width: 300px;
       display: -webkit-box;
       -webkit-box-orient: vertical;
       -webkit-line-clamp: 3; /* Truncate when no. of lines exceed 3 */
       overflow: hidden;
   }
   

   Output looks like this:

   

9. Stop overworking yourself writing top, right, bottom, left

   When working with positioned elements, you often write code like this:
   

   .some-element {
       position: absolute;
       top: 0;
       left: 0;
       right: 0;
       bottom: 0;
   }
   

   This can be simplified using an inset propety:
   

   .some-element {
       position: absolute;
       inset: 0;
   }
   

   Or if you have different values for top, right, bottom and left, you can set them respectively in the order like: inset: -10px 0px -10px 0px. This shorthand works the same way as margin.

10. Serve optimized images

    Try throttling to a slow internet in the browser Dev tools and visit a website made up of HD images like unsplash. That's how to experience the pain of your website visitors trying to enjoy your high HD content from geographical areas with slow internet.
    
    But you can provide a rescue especially with the image-set CSS trick.

    You can give options to a browser to let it decide the most appropriate image that suits a user's device. For instance:
    

    .banner {
        background-image: url("elephant.png"),
        background-image: -webkit-image-set(
            url("elephant.webp") type("image/webp") 1x,
            url("elephantHD.webp") type("image/webp") 2x,
            url("elephant.png") type("image/png") 1x,
            url("elephantHD.png") type("image/png") 2x
        );
    }
    

    The code above will set the background image of an element.
    
    If -webkit-image-set is supported, then background image will be an optimized image, i.e an image of supported MIME type and that better suits the resolution power of the user's device.
    
    For example: Since a higher quality image is directly proportional to a larger size, a user who has a high resolution device but in a poor network, will prompt the browser to decide on serving a supported image with lower resolution. Ii is logical not to make a user wait for the HD image to load.

    Note: An image that the browser decides as the best fit, is what is downloaded

11. Counters

    You don't have to get stuck on how the browser renders a numbered list. You can implement your own design utilizing counters(). Here's how:
    

    ul {
        margin: 0;
        font-family: sans-serif;
    
        /* Define & Initialize Counter */
        counter-reset: list 0;
    }
    
    ul li {
        list-style: none;
    }
    
    ul li:before {
        padding: 5px;
        margin: 0 8px 5px 0px;
        display: inline-block;
        background: skyblue;
        border-radius: 50%;
        font-weight: 100;
        font-size: 0.75rem;
    
        /* Increment counter by 1 */
        counter-increment: list 1;
        /* Show incremented count padded with `.` */
        content: counter(list) ".";
    }
    

    Output looks like this:

    

    This works for any other DOM element apart from <ul> and <ol>.

12. Form validation visual cues

    With only CSS, you can display helping visual cues to users regarding the validity of input entered in the forms. We can use :valid and :invalid CSS pseudo classes on form elements to apply appropriate styles when their contents validate successfully or not.

    Consider the following HTML page structure:
    

    <!-- Regex in pattern attribute means input can accept `firstName Lastname` (whitespace sepearated names) -->
    <!-- And invalidates any other symbols like `*` -->
    <input
        type="text"
        pattern="([a-zA-Z0-9]\s?)+"
        placeholder="Enter full name"
        required
    />
    <span></span>
    

    <span> will be used to show validation results.

    And the CSS below styles an input regarding its validation result:
    

    input + span {
        position: relative;
    }
    
    input + span::before {
        position: absolute;
        right: -20px;
        bottom: 0;
    }
    
    input:not(:placeholder-shown):invalid {
        border: 2px solid red;
    }
    
    input:not(:placeholder-shown):invalid + span::before {
        content: "✖";
        color: red;
    }
    
    input:not(:placeholder-shown):valid + span::before {
        content: "✓";
        color: green;
    }
    

    So we have achieved interactivity without consulting any javascript. A full codepen implementing this technique is shown below:

13. Select text with one click

    This trick is inclined towards improving copy and paste experience for website users. Using user-select: all, you can enable easy text selection with one click. All text node below that element is selected.

    On the other hand, you can disable text selection with user-select: none;. Alternative way to disable text selection is placing text inside content: ''; property of ::before or ::after CSS pseudo element.

Thanks for reading. See you in the next article. Follow me here on Dev to be notified.

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