button {
padding: 0;
min-width: 160px;
min-height: 50px;
opacity: 1;
white-space: nowrap;
background: linear-gradient(to top, #121212 40%, #636363 70%, #a6a6a6 90%);
border: 3px solid #4f4f4f;
border-radius: 15px;
margin: 0;
/* добавить */
display: flex;
flex-direction: row;
align-items: center;
align-content: center;
justify-content: center;
}