style.css

/*Обнуление*/
* {
  padding: 0;
  margin: 0;
  border: 0;
}
*,
*:before,
*:after {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}
:focus,
:active {
  outline: none;
}
a:focus,
a:active {
  outline: none;
}

nav,
footer,
header,
aside {
  display: block;
}

html,
body {
  height: 100%;
  width: 100%;
  font-size: 100%;
  line-height: 1;
  font-size: 14px;
  -ms-text-size-adjust: 100%;
  -moz-text-size-adjust: 100%;
  -webkit-text-size-adjust: 100%;
}
input,
button,
textarea {
  font-family: inherit;
}

input::-ms-clear {
  display: none;
}
button {
  cursor: pointer;
}
button::-moz-focus-inner {
  padding: 0;
  border: 0;
}
a,
a:visited {
  text-decoration: none;
}
a:hover {
  text-decoration: none;
}
ul li {
  list-style: none;
}
img {
  vertical-align: top;
}

h1,
h2,
h3,
h4,
h5,
h6 {
  font-size: inherit;
  font-weight: 400;
}
/*______________________________________*/

.calc {
  /* border: 1px solid red; */
  border-radius: 15px;
  height: 390px;
  width: 250px;
  background-color: black;
  margin: 0 auto;
  margin-top: 20px;
  box-shadow: 10px 5px 5px rgb(244, 198, 112);
}
.calcScreen {
  /* border: 1px solid red; */
  border-radius: 15px;
  height: 90px;
  text-align: right;
  color: white;
  padding: 40px 10px 5px 5px;
  font-size: 30px;
  margin-bottom: 0px;
}

.button {
  display: flex;
}
.btn {
  display: inline-block;
  background-color: rgb(68, 67, 67);
  width: 50px;
  height: 50px;
  border-radius: 50%;
  text-align: center;
  margin: 4px;
  padding-top: 15px;
  font-size: 20px;
}
.num {
  background-color: gray;
}
.acshen {
  background-color: orange;
}

.zero {
  height: 50px;
  width: 110px;
  border-radius: 25px;
}