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Make fancy, revealing animations with these simple CSS tricks

Carlos Roso

A life-changing approach to CSS transitions.

I hate clickbait articles as much as you do, but this isn’t one of those. So, let me save you a 10-minute read by just spitting out the tricks right here, right now.

  • Define a handful of CSS animations with @keyframes
  • Set the element’s initial state (opacity:0, scale(0), etc.)
  • Set the element’s animation CSS property to be one of the animations you just defined.
  • Set the animation’s fill-mode to forwards.
  • Don’t always use the good old ease timing function but instead try some cool cubic-bezier.
  • Orchestrate the whole thing via animation-delay.
  • Keep it clean and classy by avoiding wide range of movements.
  • Only animate transform and opacity.
  • Always strive for 60fps.

Easy, huh? This framework is obviously agnostic as the element’s animation will trigger once it’s inserted into the DOM or its display property goes from none to visible. This is the normal behavior of any framework’s router, so you’ll be good to go regardless of your preferred frontend stack.

Thanks for reading!

Wait, it seems you want some more detail, some more meat. That’s cool, I can do that as well.

In the next couple of paragraphs, I’ll explain to you in more detail how to easily achieve the animation shown above.

Mastering the technique

Reveal that header

We’ll start by first identifying the three agents we want to independently animate:We basically have 3 agents that we want to reveal at different times. In blue, I have colored the time offset in which each agent should reveal itself. We want Agent 1 and Agent 3 to subtly fade-in from the left. For Agent 2, it makes sense to have a cool enlarge animation from left to right as if the line was flowing from Agent 1 to Agent 3. Let’s start by defining our core CSS animations:

@keyframes fade-in-right {
  from {
    opacity: 0;
    transform: translateX(-15px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

@keyframes grow-left {
  from {
    transform: scaleX(0);
  }
  to {
    transform: scaleX(1);
  }
}

For fade-in-right, we define our element’s initial state as hidden and moved a bit to the left. Our final state will render our element to full opacity and locate it back to its natural position. Look how I go with just 15px of movement range.

Always avoid long-range movements; the whole secret lies in small, subtle motion.

The code for grow-left is pretty self-explanatory so I won’t go into details. The cool thing here is to see that I’m only animating the following two CSS properties: transform and opacity.

Now that we defined our animations, let’s apply them to our agents. Three important things you need to keep in mind before looking at the code:

  1. Set the initial state of the element in its default CSS properties.
  2. Use forwards as the fill mode of the animation so that it preserves its final state.
  3. Orchestrate revealings via animation-delay
.agent-1, .agent-3 {
  opacity: 0;
  animation: fade-in-right ease 0.4s forwards;
}

.agent-2 {
  transform: scaleX(0);
  transform-origin: left;
  animation: grow-left cubic-bezier(0.785, 0.135, 0.15, 0.86) 0.5s forwards;
  animation-delay: 0.4s;
}

.agent-3 {
  animation-delay: 0.8s;
}

We defined the initial state for agents 1 and 3 as opacity: 0 because we want them to be hidden until the fade-in transition comes in. Then, we set the animation to be the previously defined fade-in-right with the ease function and forwards fill-mode. Since we still want Agent 3 to make its entrance to the scene later on, we set an animation-delay: 0.8s – this means that the animation won’t start up until 800 ms have passed since the element was placed on the DOM or was made visible via display property.

Now, for Agent 2 things are a bit different. The initial state is set to transform: scaleX(0), otherwise our element will be shown as fully enlarged until the animation kicks in. So, by setting an initial set, we’re indicating how the element should render even before the animation is fired. Then, we set its transform-origin: left property so that the line enlarges from left to right; otherwise, its anchor would be the center by default. We then do something similar as with agents 1 and 3 by setting animation: grow-left, setting its fill mode to forwards, and making sure it reveals itself after only 0.4 seconds of being rendered in the DOM. The interesting bit here is the fact that we’re not using the default ease function as our animation timing function, but instead, we are defining a custom cubic-bezier function. This allows us to create more interesting and visually appealing transitions than those coming by default in the browser. Go ahead and try defining your own cubic-bezier with this fun tool.

Let’s see the final result:

Pretty cool, huh? See how the animation-delay makes a lot of sense now and how agents 1 and 3 both have the same revealing motion?

Coming up with the right animation durations and animation delays is a matter of trial and error, so don’t stress too much about it and just have fun playing with it.

Show me the body now

It really makes no sense to go through the process of animating the rest of the content as the same technique repeats over and over again. So:

  1. Identify agents and revealing timings
  2. Create appropriate animations
  3. Set initial states to agents
  4. Set animations to each agent and orchestrate via proper animation delays
  5. Tune the animation by trial and error
  6. Profit

Cool, but, you know, #perfmatters

Yeah, perf matters, and that’s why we strive to run the whole show with just transform and opacity. These are the only properties that trigger compositing in the browser rendering process and, thus, avoid computing work to result in a jank free experience.

Let’s run a perf profiling on our revealing animation:

Go ahead and look at that green bar. This means that 99% of the time we hit 60fps in the whole animation. 60 frames per second! It can’t really be more performant. Please keep in mind that the more elements you animate (known as agents in this article), the jankier your app will look like even when using the CSS golden props. This is because every animation will inevitably add a bit of GPU workload. So, try pushing to limit the number of animated elements, but always strive to hit the 60fps mark.

Too much magic

“I’m not creative enough to come up with fancy animations like these.”

Building great animations is not a matter of being technically competent, instead it takes quite a good sense of design and an innate drive to craft good UI interactions. This can be very difficult and only the most talented designers are creative enough to accomplish such feats. However, we mortals are still able to learn by imitating and taking as much inspiration as we can from true pros. For this, I recommend that you frequently visit sites like Awwwards or Dribbble and check ideas on cool page revealing animations.

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Carlos Roso
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