styles.css

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  font-family: Poppins, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 'Helvetica Neue', sans-serif;
}

::selection {
  display: none;
}

:root {
  --white-soft: rgba(255, 255, 255, 0.35);
  --white-light: rgba(255, 255, 255, 0.5);
  --white: rgba(255, 255, 255, 0.8);
  --black: #32292F;
  --first-color: #35A7FF;
  --second-color: #44CF6C;
}

body {
  display: grid;
  height: 100vh;
  width: 100vw;
  align-items: center;
  justify-items: center;
  overflow: hidden;
  color: var(--black);
  background: linear-gradient(120deg, var(--first-color), var(--first-color) 25%, var(--second-color) 75%, var(--second-color));
}

button,
input {
  cursor: pointer;
  padding: 8px 16px;
  border: none;
  width: 100%;
  background-color: transparent;
  border-bottom: 1px solid var(--white-soft);
  border-right: 1px solid var(--white-soft);
}

button:hover,
input:hover {
  background-color: var(--white-light);
}

button:disabled,
input:disabled {
  cursor: default;
}

button:disabled:hover,
input:disabled:hover {
  background-color: inherit;
}

input {
  width: 100%;
  cursor: text;
}

input:focus {
  outline: none;
  background-color: var(--white);
}

input:disabled:focus {
  background-color: inherit;
}

.timer {
  width: 280px;
  background-color: var(--white-soft);
  backdrop-filter: blur(20px);
  border-top: 1px solid var(--white-soft);
  border-left: 1px solid var(--white-soft);
  box-shadow: 5px 5px 30px var(--white-light);
  border-radius: 10px;
  overflow: hidden;
  transition: all 0.6s ease-in-out;
}

.timer:hover {
  box-shadow: 5px 5px 30px var(--white-soft);
  margin-bottom: 15px;
}

.timer__default-custom {
  text-align: center;
  padding-left: 32px;
}

.timer__time {
  font-size: 4rem;
  font-weight: bold;
  display: flex;
  justify-content: center;
  cursor: default;
  border-bottom: 1px solid var(--white-soft);
  border-right: 1px solid var(--white-soft);
}

.timer__controls,
.timer__default {
  display: flex;
  justify-content: space-between;
  align-items: center;
}