<div class='support-grid'></div>
<section class='grid-1'>
  <div class='title'>
    <img src='https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/merry-xmas.svg'>
  </div>
  <div class='day-1'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>1</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-2'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>2</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-3'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>3</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-4'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>4</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-5'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>5</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-6'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>6</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-7'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>7</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-8'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>8</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-9'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>9</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-10'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>10</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-11'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>11</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-12'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>12</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-13'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>13</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-14'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>14</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-15'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>15</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-16'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>16</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-17'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>17</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-18'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>18</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-19'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>19</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-20'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>20</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-21'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>21</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-22'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>22</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-23'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>23</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
  <div class='day-24'>
    <label>
      <input type='checkbox'>
        <div class='door'>
          <div class='front'>24</div>
          <div class='back'></div>
        </div>
      </input>
    </label>
  </div>
</section>
<footer><a href='http://webdesign.tutsplus.com/tutorials/how-to-build-a-festive-advent-calendar-with-css-grid--cms-30070'>
    Envato Tuts+ 2017 ☃️
  </a>
</footer>
body {
  background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/snow-bg.svg) no-repeat top center #82d8cb;
  background-size: cover;
}

/* title graphic */
.title {  
  display: flex;
  align-items: center;
  justify-content: center; 
}

.title img {
  width: 90%;
  height: auto;
}

/* mobile first grid layout */
.grid-1 {
  display: grid;
  width: 96%;
  max-width: 900px;
  margin: 2% auto;
  
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: auto;
  grid-gap: 25px;
  
  grid-template-areas:    "t        t       t"
                          "d23      d20     d12"
                          "d2       d14     d4"
                          "d5       d22     d16"
                          "d1       d7      d9"
                          "d10      d11     d18"
                          "d13      d3      d15"
                          "d6       d17     d8"
                          "d19      d24     d21";
}

/* media query */
@media only screen and (min-width: 500px) {
  
  .grid-1 {
    grid-template-columns: repeat(6, 1fr);
    grid-template-areas: "t     t     t     d2      d7      d8"
                         "t     t     t     d4      d11     d12"
                         "t     t     t     d19     d9      d13"
                         "d6    d1    d24   d24     d21     d20"
                         "d17   d18   d24   d24     d5      d22"
                         "d3    d23   d16   d14     d10     d15";
  }
  
}


/* individual items */
  .title {
    grid-area: t;
  }
  .day-1 {
  grid-area: d1;
  }
  .day-1 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/child.svg);
  }
  .day-2 {
    grid-area: d2;
  }
  .day-2 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/donut.svg);
  }
  .day-3 {
    grid-area: d3;
  }
  .day-3 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/santa.svg);
  }
  .day-4 {
    grid-area: d4;
  }
  .day-4 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/child-3.svg);
  }
  .day-5 {
    grid-area: d5;
  }
  .day-5 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/book.svg);
  }
  .day-6 {
    grid-area: d6;
  }
  .day-6 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/snowflake.svg);
  }
  .day-7 {
    grid-area: d7;
  }
  .day-7 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/gift.svg);
  }
  .day-8 {
    grid-area: d8;
  }
  .day-8 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/stocking.svg);
  }
  .day-9 {
    grid-area: d9;
  }
  .day-9 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/gift.svg);
  }
  .day-10 {
    grid-area: d10;
  }
  .day-10 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/bird.svg);
  }
  .day-11 {
    grid-area: d11;
  }
  .day-11 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/snowman.svg);
  }
  .day-12 {
    grid-area: d12;
  }
  .day-12 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/child-2.svg);
  }
  .day-13 {
    grid-area: d13;
  }
  .day-13 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/holly.svg);
  }
  .day-14 {
    grid-area: d14;
  }
  .day-14 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/horse.svg);
  }
  .day-15 {
    grid-area: d15;
  }
  .day-15 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/book.svg);
  }
  .day-16 {
    grid-area: d16;
  }
  .day-16 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/bird.svg);
  }
  .day-17 {
    grid-area: d17;
  }
  .day-17 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/stocking.svg);
  }
  .day-18 {
    grid-area: d18;
  }
  .day-18 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/donut.svg);
  }
  .day-19 {
    grid-area: d19;
  }
  .day-19 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/child.svg);
  }
  .day-20 {
    grid-area: d20;
  }
  .day-20 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/holly.svg);
  }
  .day-21 {
    grid-area: d21;
  }
  .day-21 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/snowflake-2.svg);
  }
  .day-22 {
    grid-area: d22;
  }
  .day-22 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/santa.svg);
  }
  .day-23 {
    grid-area: d23;
  }
  .day-23 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/child-2.svg);
  }
  .day-24 {
    grid-area: d24;
  }
  .day-24 .back {
    background: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/210284/tree.svg);
  }


/* door styles */

.grid-1 input {
  display: none;
}

label {
  perspective: 1000px;
  transform-style: preserve-3d;
  cursor: pointer;

  display: flex;
  min-height: 100%;
  width: 100%;
  height: 120px;
}

.door {
  width: 100%;
  transform-style: preserve-3d;
  transition: all 300ms;
  border: 2px dashed transparent;
  border-radius: 10px;
}

  .door div {
    position: absolute;
    height: 100%;
    width: 100%;
    backface-visibility: hidden;
    
    border-radius: 6px;

    display: flex;
    align-items: center;
    justify-content: center;
    
    /* typography */
    font-family: 'Kalam', cursive;
    color: #385052;
    font-size: 2em;
    font-weight: bold;
    text-shadow: 1px 1px 0 rgba(255, 255, 255, 0.2);
  }

  .door .back {
      background-size: contain;
      background-position: center center;
      background-repeat: no-repeat;
      background-color: #2e313d;
      transform: rotateY(180deg);
  }

  label:hover .door {
    border-color: #385052;
  }

  :checked + .door {
    transform: rotateY(180deg);
  }


/* footer styles */
footer {
  text-align: center;
  padding: 2em 0;
}  
  footer a {
      color: #2e313d;
  } 
    footer a:hover {
          text-decoration: none;
    }

External CSS

  1. https://codepen.io/tutsplus/pen/ZpvWBO

External JavaScript

This Pen doesn't use any external JavaScript resources.