html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, dl, dt, dd, ol, ul, li, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td, article, aside, canvas, details, embed, figure, figcaption, footer, header, hgroup, menu, nav, output, ruby, section, summary, time, mark, audio, video {
  margin: 0;
  padding: 0;
  border: 0;
  font-size: 100%;
  font: inherit;
  vertical-align: baseline;
}

/* HTML5 display-role reset for older browsers */

article, aside, details, figcaption, figure, footer, header, hgroup, menu, nav, section {
  display: block;
}

body {
  line-height: 1;
}

ol, ul {
  list-style: none;
}

blockquote, q {
  quotes: none;
}

blockquote:before, blockquote:after, q:before, q:after {
  content: '';
  content: none;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

header {
  margin: 30px 0 30px 0;
}



#app {
  display: flex;
  flex-direction: column;
  align-items: center;
}

header {
  width: 800px;
  display: flex;
  justify-content: center;
  align-items: center;
}

h1 {
  font-size: 60px;
}

.content {
  width: 800px;
}

.content>ul {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
}

.content>ul>li {
  font-size: 40px;
  margin: 20px;
  padding: 20px;
  border: aquamarine 2px solid;
  user-select: none;
}

li.active {
  text-decoration: line-through;
  background-color: darkgray;
}

.counting{
  width:60px ;
  font-size: 60px;
  margin-left: 30%;

}

@media (max-width: 400px){
  header {
    width: 300px;
    margin: 10px 0;
  }
  .counting{
    font-size: 30px;
    margin-left: 10%;
    
  }
  .content {
    width: 350px;
  }
  .content>ul>li {
    font-size: 35px;
    margin: 7px;
    padding: 7px;
  }
  h1 {
    font-size: 40px;
  }
}