JSFiddle - React, Tailwind, and code Playground

HTML

<form action="" class="my-form">
			<input type="text" class="my-form_imput" placeholder="Имя">
			<input type="text" class="my-form_imput" placeholder="Телефон">
			<input type="text" class="my-form_imput" placeholder="Email">
		  <button type="submit" class="my-form_btn">Войти</button>
	</form>

CSS

.my-form {
	max-width: 980px;
  background: rgba(4, 4, 4, 0.78);
  padding: 20px;
}

input, button {
  box-sizing: border-box;
  width: 100%;
  margin-bottom: 10px; /* Тут сам играйся с отступами */
   padding: 10px; /* Тут сам играйся с отступами */
}
		
@media (min-width: 768px) {
  input, button {
    width: 24.5%;
  }  
}