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HTML 

              
                <div class="preload" >
  <div class="doors">
      <div class="left-side"></div>
    <div class="right-side"></div>
  </div>
  <div class="circle__1">
  </div>
  <div class="circle__2">
  </div>
  <div class="circle__3">
  </div>
</div>

<div class="content">
  <h1>Lorem ipsum dolor sit amet consectetur, adipisicing elit. Animi vero nesciunt modi, incidunt ea similique reiciendis provident eligendi suscipit omnis.</h1>
  <p>Lorem ipsum dolor sit amet consectetur adipisicing elit. Maiores odit accusamus ipsa velit consequatur porro dolores at voluptatum. Obcaecati ipsa earum fugit. Rem ad quidem quos vel assumenda aperiam, unde, maxime ipsum natus laborum vero quia consequatur accusamus explicabo ullam aliquid iste similique officiis nihil, voluptate quasi recusandae. Labore voluptas facilis molestias corrupti explicabo mollitia earum cum, eius commodi neque saepe vitae aliquam quis id. Necessitatibus delectus doloribus officia ducimus sequi, error itaque repellat accusantium repellendus? Tenetur repellat obcaecati, perspiciatis accusamus ipsum excepturi nesciunt autem distinctio dolore quis qui facilis necessitatibus dolorum doloribus libero est mollitia saepe minus beatae quae expedita soluta ex ducimus. Blanditiis fugiat non officia illum. Iusto, eos dolores rerum necessitatibus eaque odio, atque, inventore amet neque libero modi ut blanditiis corrupti nam harum repellat soluta officiis tempore iste est natus omnis. Omnis nisi, fugit molestias minus recusandae quos. Reiciendis laudantium dicta natus? Iste eaque placeat cumque adipisci deleniti recusandae, labore velit, totam quaerat, error debitis ipsa ratione neque! Porro suscipit laboriosam minima, possimus facilis esse, rerum, error nesciunt repellat ipsum necessitatibus? Similique, sapiente aliquid. Non quisquam laudantium, ipsa minus eaque laboriosam deserunt neque eveniet quae porro quod, dolor corporis! Praesentium cupiditate, itaque libero eum perspiciatis quod.</p>
</div>
!

CSS 

              
                * {
	margin: 0;
	padding: 0;
	box-sizing: border-box;
	font-size: 22px;
	font-family: 'Poppins', sans-serif;
}
:root {
	--primary: #2e2e2e;
	--secondary: #252525;
	--elem-color: #1b1b1b;
	--text: #b8b8b8;
	--accent-color: #ffa600;
	--shadow-color: rgba(0, 0, 0, 0.719);
}
body {
	background-color: var(--primary);
	display: flex;
	justify-content: center;
	align-items: center;
	height: 100vh;
}
.preload {
	width: 100%;
	height: 100vh;
	position: fixed;
	top: 0;
	display: flex;
	justify-content: center;
	align-items: center;
	flex-direction: column;

	@for $i from 1 through 3 {
		.circle__#{$i} {
			border: 4px solid;
			border-radius: 50%;
			position: absolute;
			filter: drop-shadow(0px 0px 5px var(--accent-color));
			width: 250px - $i * 50px;
			aspect-ratio: 1 / 1;
			animation: 1.4s - $i * 0.2s spin linear infinite;
		}
	}
	.circle {
		&__1 {
			border-color: var(--accent-color) var(--accent-color) var(--accent-color) transparent;
		}
		&__2 {
			border-color: transparent transparent var(--accent-color) var(--accent-color);
		}
		&__3 {
			border-color: var(--accent-color) transparent transparent var(--accent-color);
		}
	}
	&.finished {
		@for $i from 1 through 3 {
			.circle__#{$i} {
				opacity: 0;
				transition: 400ms linear;
			}
		}
		.doors {
			.left-side {
				transform: translateX(-100%);
				transition: 1000ms ease-in-out 500ms;
			}
			.right-side {
				transform: translateX(100%);
				transition: 1000ms ease-in-out 500ms;
			}
		}
	}
	.doors {
		width: 100%;
		height: 100%;
		display: flex;
		flex-direction: row;
		.left-side {
			background-color: var(--elem-color);
			height: 100%;
			width: 50%;
			border-top: 1px solid var(--accent-color);
		}
		.right-side {
			background-color: var(--elem-color);
			height: 100%;
			width: 50%;
			border-top: 1px solid var(--accent-color);
		}
	}
}
.content {
	margin: 0 auto;
	margin-top: 100px;
	padding: 20px;
	width: min(calc(100% - 2rem), 1000px);
	background-color: var(--secondary);
	display: flex;
	justify-content: center;
	align-items: center;
	flex-direction: column;
	border-radius: 8px;
	box-shadow: 0px 5px 25px var(--shadow-color);
	h1 {
		color: var(--accent-color);
		font-size: 1.4rem;
	}
	p {
		margin-top: 30px;
		color: var(--text);
	}
}
@keyframes spin {
	from {
		transform: rotate(0deg);
	}
	to {
		transform: rotate(360deg);
	}
}
!

JS 

              
                window.addEventListener('load', () => {
  setTimeout(() => {
    document.querySelector('.preload').classList.add('finished')
  }, 1000);
});
!
999px

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