Coin Flip Donate Button

coin-flip-donate-button.markdown

Coin Flip Donate Button

A simple idea that ended up being really hard to pull off. No 3D elements or transformations are used in this experiment, only 2D elements and some clever math to give the illusion of a 3D coin with real thickness. I'm happy with the results given the limitations of HTML and CSS.

The coin flipping is actually randomized too -- if you press the button a few times you'll see.

A Pen by Cooper Goeke on CodePen.

License.

index.html

<button class="tip-button">
  <span class="tip-button__text">Send me a tip</span>
  <div class="coin-wrapper">
    <div class="coin">
      <div class="coin__middle"></div>
      <div class="coin__back"></div>
      <div class="coin__front"></div>
    </div>
  </div>
</button>

script.js

const tipButtons = document.querySelectorAll('.tip-button')

// Loop through all buttons (allows for multiple buttons on page)
tipButtons.forEach((button) => {
  let coin = button.querySelector('.coin')

  // The larger the number, the slower the animation
  coin.maxMoveLoopCount = 90

  button.addEventListener('click', () => {
    if (button.clicked) return

    button.classList.add('clicked')

    // Wait to start flipping the coin because of the button tilt animation
    setTimeout(() => {
      // Randomize the flipping speeds just for fun
      coin.sideRotationCount = Math.floor(Math.random() * 5) * 90
      coin.maxFlipAngle = (Math.floor(Math.random() * 4) + 3) * Math.PI
      button.clicked = true
      flipCoin()
    }, 50)
  })

  const flipCoin = () => {
    coin.moveLoopCount = 0
    flipCoinLoop()
  }

  const resetCoin = () => {
    coin.style.setProperty('--coin-x-multiplier', 0)
    coin.style.setProperty('--coin-scale-multiplier', 0)
    coin.style.setProperty('--coin-rotation-multiplier', 0)
    coin.style.setProperty('--shine-opacity-multiplier', 0.4)
    coin.style.setProperty('--shine-bg-multiplier', '50%')
    coin.style.setProperty('opacity', 1)
    // Delay to give the reset animation some time before you can click again
    setTimeout(() => {
      button.clicked = false
    }, 300)
  }

  const flipCoinLoop = () => {
    coin.moveLoopCount++
    let percentageCompleted = coin.moveLoopCount / coin.maxMoveLoopCount
    coin.angle = -coin.maxFlipAngle * Math.pow((percentageCompleted - 1), 2) + coin.maxFlipAngle
    
    // Calculate the scale and position of the coin moving through the air
    coin.style.setProperty('--coin-y-multiplier', -11 * Math.pow(percentageCompleted * 2 - 1, 4) + 11)
    coin.style.setProperty('--coin-x-multiplier', percentageCompleted)
    coin.style.setProperty('--coin-scale-multiplier', percentageCompleted * 0.6)
    coin.style.setProperty('--coin-rotation-multiplier', percentageCompleted * coin.sideRotationCount)

    // Calculate the scale and position values for the different coin faces
    // The math uses sin/cos wave functions to similate the circular motion of 3D spin
    coin.style.setProperty('--front-scale-multiplier', Math.max(Math.cos(coin.angle), 0))
    coin.style.setProperty('--front-y-multiplier', Math.sin(coin.angle))

    coin.style.setProperty('--middle-scale-multiplier', Math.abs(Math.cos(coin.angle), 0))
    coin.style.setProperty('--middle-y-multiplier', Math.cos((coin.angle + Math.PI / 2) % Math.PI))

    coin.style.setProperty('--back-scale-multiplier', Math.max(Math.cos(coin.angle - Math.PI), 0))
    coin.style.setProperty('--back-y-multiplier', Math.sin(coin.angle - Math.PI))

    coin.style.setProperty('--shine-opacity-multiplier', 4 * Math.sin((coin.angle + Math.PI / 2) % Math.PI) - 3.2)
    coin.style.setProperty('--shine-bg-multiplier', -40 * (Math.cos((coin.angle + Math.PI / 2) % Math.PI) - 0.5) + '%')

    // Repeat animation loop
    if (coin.moveLoopCount < coin.maxMoveLoopCount) {
      if (coin.moveLoopCount === coin.maxMoveLoopCount - 6) button.classList.add('shrink-landing')
      window.requestAnimationFrame(flipCoinLoop)
    } else {
      button.classList.add('coin-landed')
      coin.style.setProperty('opacity', 0)
      setTimeout(() => {
        button.classList.remove('clicked', 'shrink-landing', 'coin-landed')
        setTimeout(() => {
          resetCoin()
        }, 300)
      }, 1500)
    }
  }
})

style.scss

$coin-size: 3.5rem;
$coin-thickness: $coin-size / 11;

$bg: #f4f7ff;
$bg-button: #031032;
$font-color: #fff;
$c-l: #fcfaf9;
$c-m: #c2cadf;
$c-d: #8590b3;
$c-side: #737c99;
$shine: #e9f4ff;

.tip-button {
  background: none;
  border: 0;
  border-radius: 0.25rem 0.25rem 0 0;
  cursor: pointer;
  font-family: 'Quicksand', sans-serif;
  font-size: 0.75rem;
  font-weight: 600;
  height: 2.6rem;
  margin-bottom: -4rem;
  outline: 0;
  position: relative;
  top: 0;
  transform-origin: 0% 100%;
  transition: transform 50ms ease-in-out;
  width: 9.5rem;
  -webkit-tap-highlight-color: transparent;
  &:active {
    transform: rotate(4deg);
  }
  // Button was clicked
  &.clicked {
    animation: 150ms ease-in-out 1 shake;
    pointer-events: none;
    .tip-button__text {
      opacity: 0;
      transition: opacity 100ms linear 200ms;
    }
    &::before { // background/bar
      height: 0.5rem;
      width: 60%;
    }
    .coin {
      transition: margin-bottom 1s linear 200ms;
      margin-bottom: 0;
    }
  }
  // Coin almost finished falling
  &.shrink-landing {
    &::before { // background/bar
      transition: width 200ms ease-in;
      width: 0;
    }
  }
  // Coin finished falling
  &.coin-landed {
    &::after { // Thank you message
      opacity: 1;
      transform: scale(1);
      transform-origin: 50% 100%;
    }

    // Make the little confetti looking dots on this wrapper
    .coin-wrapper {
      background:
        radial-gradient(circle at 35% 97%, rgba($bg-button, 0.4) 0.04rem, transparent 0.04rem),
        radial-gradient(circle at 45% 92%, rgba($bg-button, 0.4) 0.04rem, transparent 0.02rem),
        radial-gradient(circle at 55% 98%, rgba($bg-button, 0.4) 0.04rem, transparent 0.04rem),
        radial-gradient(circle at 65% 96%, rgba($bg-button, 0.4) 0.06rem, transparent 0.06rem);
      background-position: center bottom;
      background-size: 100%;
      bottom: -1rem;
      opacity: 0;
      transform: scale(2) translateY(-10px);
    }
  }

  &__text {
    color: $font-color;
    margin-right: 1.8rem;
    opacity: 1;
    position: relative;
    transition: opacity 100ms linear 500ms;
    z-index: 3;
  }

  // Background of button
  &::before {
    background: $bg-button;
    border-radius: 0.25rem;
    bottom: 0;
    content: '';
    display: block;
    height: 100%;
    left: 50%;
    position: absolute;
    transform: translateX(-50%);
    transition: height 250ms ease-in-out 400ms, width 250ms ease-in-out 300ms;
    width: 100%;
    z-index: 2;
  }

  // Thank you message
  &::after {
    bottom: -1rem;
    color: $bg-button;
    content: 'Thank you!';
    height: 110%;
    left: 0;
    opacity: 0;
    position: absolute;
    pointer-events: none;
    text-align: center;
    transform: scale(0);
    transform-origin: 50% 20%;
    transition: transform 200ms cubic-bezier(0,0,.35,1.43);
    width: 100%;
    z-index: 1;
  }
}

.coin-wrapper {
  background: none;
  bottom: 0;
  height: 18rem;
  left: 0;
  opacity: 1;
  overflow: hidden;
  pointer-events: none;
  position: absolute;
  transform: none;
  transform-origin: 50% 100%;
  transition: opacity 200ms linear 100ms, transform 300ms ease-out;
  width: 100%;
}

.coin {
  --front-y-multiplier: 0;
  --back-y-multiplier: 0;
  --coin-y-multiplier: 0;
  --coin-x-multiplier: 0;
  --coin-scale-multiplier: 0;
  --coin-rotation-multiplier: 0;
  --shine-opacity-multiplier: 0.4;
  --shine-bg-multiplier: 50%;
  bottom: calc(var(--coin-y-multiplier) * 1rem - #{$coin-size});
  height: $coin-size;
  margin-bottom: 3.05rem;
  position: absolute;
  right: calc(var(--coin-x-multiplier) * 34% + 16%);
  transform:
    translateX(50%)
    scale(calc(0.4 + var(--coin-scale-multiplier)))
    rotate(calc(var(--coin-rotation-multiplier) * -1deg));
  transition: opacity 100ms linear 200ms;
  width: $coin-size;
  z-index: 3;

  &__front,
  &__middle,
  &__back,
  &::before,
  &__front::after,
  &__back::after {
    border-radius: 50%;
    box-sizing: border-box;
    height: 100%;
    left: 0;
    position: absolute;
    width: 100%;
    z-index: 3;
  }

  // Tails
  &__front {
    background:
      radial-gradient(circle at 50% 50%, transparent 50%, rgba($c-side, 0.4) 54%, $c-m 54%),
      linear-gradient(210deg, $c-d 32%, transparent 32%),
      linear-gradient(150deg, $c-d 32%, transparent 32%),
      linear-gradient(to right, $c-d 22%, transparent 22%, transparent 78%, $c-d 78%),
      linear-gradient(to bottom, $c-l 44%, transparent 44%, transparent 65%, $c-l 65%, $c-l 71%, $c-d 71%),
      linear-gradient(to right, transparent 28%, $c-l 28%, $c-l 34%, $c-d 34%, $c-d 40%, $c-l 40%, $c-l 47%, $c-d 47%, $c-d 53%, $c-l 53%, $c-l 60%, $c-d 60%, $c-d 66%, $c-l 66%, $c-l 72%, transparent 72%);
    background-color: $c-d;
    background-size: 100% 100%;
    transform: translateY(calc(var(--front-y-multiplier) * #{$coin-thickness} / 2)) scaleY(var(--front-scale-multiplier));
  
    // Shadow on coin face
    &::after {
      background: rgba(#000, 0.2);
      content: '';
      opacity: var(--front-y-multiplier);
    }
  }

  &__middle {
    background: $c-side;
    transform: translateY(calc(var(--middle-y-multiplier) * #{$coin-thickness} / 2)) scaleY(var(--middle-scale-multiplier));
  }

  // Heads
  &__back {
    background:
      radial-gradient(circle at 50% 50%, transparent 50%, rgba($c-side, 0.4) 54%, $c-m 54%),
      radial-gradient(circle at 50% 40%, $c-l 23%, transparent 23%),
      radial-gradient(circle at 50% 100%, $c-l 35%, transparent 35%);
    background-color: $c-d;
    background-size: 100% 100%;
    transform: translateY(calc(var(--back-y-multiplier) * #{$coin-thickness} / 2)) scaleY(var(--back-scale-multiplier));
  
    // Shadow on coin face
    &::after {
      background: rgba(#000, 0.2);
      content: '';
      opacity: var(--back-y-multiplier);
    }
  }

  // Light glare on the coin
  &::before {
    background:
      radial-gradient(circle at 25% 65%, transparent 50%, rgba(white, 0.9) 90%),
      linear-gradient(55deg, transparent calc(var(--shine-bg-multiplier) + 0%), $shine calc(var(--shine-bg-multiplier) + 0%), transparent calc(var(--shine-bg-multiplier) + 50%));
    content: '';
    opacity: var(--shine-opacity-multiplier);
    transform:
      translateY(calc(var(--middle-y-multiplier) * #{$coin-thickness} / -2))
      scaleY(var(--middle-scale-multiplier))
      rotate(calc(var(--coin-rotation-multiplier) * 1deg));
    z-index: 10;
  }

  // Sqaure for the 'side' of the coin
  &::after {
    background: $c-side;
    content: '';
    height: $coin-thickness;
    left: 0;
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    width: 100%;
    z-index: 2;
  }
}

@keyframes shake {
  0% { transform: rotate(4deg) }
  66% { transform: rotate(-4deg) }
  100% { transform: rotate() }
}

/********* BODY STYLES *********/
html,
body {
  height: 100%;
}

body {
  align-items: center;
  background: $bg;
  display: flex;
  justify-content: center;
  -webkit-font-smoothing: antialiased;
}