style.css

@import url("https://fonts.googleapis.com/css2?family=Open+Sans:wght@300;400;600;700&display=swap");

:root {
  --white: #fff;
  --black: #1c2b2d;
  --blue: #31326f;
  --light-blue: #39286a;
  --color-primary: #9d0191;
  --color-sec: #db6400;
  --grey: #eee;
  --dark-grey: #222831;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
  
  
}

#particles-js {
  width: 100%;
  height: 100vh;
  
}


html {
  font-size: 10px;
}

body {
  font-family: "Open Sans", sans-serif;
  background-color: rgb(0, 126, 244);
  overflow: hidden;
  background-image: url(cool-background.png);
  background-size: cover;
}



p {
  font-size: 1.6rem;
  line-height: 1.5;
}

img {
  width: 100%;
}

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 20px;
  display:flex;
  flex-direction: column;
  justify-content: top;
  align-items: center;
  height: 100vh;
}


.counter-div{
  width: 40rem;
  border: 1px solid var(--grey);
  padding: 1rem;
  background-color: var(--light-blue);
  color: var(--white);
  text-align: center;
  border-radius: 5px;
}

.counter-div > *{
  margin-bottom: 2rem;
}

.count{
  font-size: 4rem;
}

.buttons button{
  padding: 1rem;
  margin: 0 1rem;
  font-size: 1.5rem;
  border: none;
  outline: none;
  border-radius: 3px;
  cursor: pointer;
}

button.subtract {
  background-color: orangered;
}

button.reset {
  background-color: var(--white);
  color: var(--black);
}

button.add {
  background-color: green;
}


Version 1.0 @PranshuBask copyright