npm install styled-components

import styled from "styled-components";

const Title = styled.h1`
  color: #e11d48;
  font-size: 30px;
  font-weight: bold;
`;

function App() {
  return <Title>سلام دنیا</Title>;
}

const Button = styled.button`
  background-color: ${(props) => (props.$primary ? "blue" : "gray")};
  color: white;
  padding: 10px 16px;
  border: none;
  border-radius: 6px;
  cursor: pointer;
`;

function App() {
  return (
    <>
      <Button $primary>دکمه اصلی</Button>
      <Button>دکمه معمولی</Button>
    </>
  );
}

const Button = styled.button`
  padding: 10px;
  border: none;
`;

const DangerButton = styled(Button)`
  background-color: red;
  color: white;
`;

const Box = styled.div`
  width: ${(props) => props.size}px;
  height: ${(props) => props.size}px;
  background-color: #22c55e;
`;

function App() {
  return <Box size={100} />;
}