<div class="container">
	
	<h1>SVG Animated Birds</h1>
	
	<div class="bird-container bird-container--one">
		<div class="bird bird--one"></div>
	</div>
	
	<div class="bird-container bird-container--two">
		<div class="bird bird--two"></div>
	</div>
	
	<div class="bird-container bird-container--three">
		<div class="bird bird--three"></div>
	</div>
	
	<div class="bird-container bird-container--four">
		<div class="bird bird--four"></div>
	</div>
	
</div>

@import url('https://fonts.googleapis.com/css?family=Arima+Madurai:300');

*,
*::before,
*::after {
	box-sizing: border-box;
}

h1 {
	font-family: 'Arima Madurai', cursive;
	color: black;
	font-size: 4rem;
	letter-spacing: -3px;
	text-shadow: 0px 1px 1px rgba(255,255,255,0.6);
	position: relative;
	z-index: 3;
}

.container {
	z-index: 1;
	position: relative;
	overflow: hidden;
	display: flex;
	align-items: center;
	justify-content: center;
	// min-height: 100vh;
	min-height: 35rem;
	background-image: linear-gradient(to bottom,  rgba(255,168,76,0.6) 0%,rgba(255,123,13,0.6) 100%), url('https://images.unsplash.com/photo-1446824505046-e43605ffb17f');
	background-blend-mode: soft-light;
	background-size: cover;
	background-position: center center;
	padding: 2rem;
}

.bird {
	background-image: url(https://s3-us-west-2.amazonaws.com/s.cdpn.io/174479/bird-cells-new.svg);
	background-size: auto 100%;
	width: 88px;
	height: 125px;
	will-change: background-position;
	
	animation-name: fly-cycle;
	animation-timing-function: steps(10);
	animation-iteration-count: infinite;

	&--one {
		animation-duration: 1s;
		animation-delay: -0.5s;		
	}
	
	&--two {
		animation-duration: 0.9s;
		animation-delay: -0.75s;
	}
	
	&--three {
		animation-duration: 1.25s;
		animation-delay: -0.25s;
	}
	
	&--four {
		animation-duration: 1.1s;
		animation-delay: -0.5s;
	}

}

.bird-container {
	position: absolute;
	top: 20%;
	left: -10%;
	transform: scale(0) translateX(-10vw);
	will-change: transform;
	
	animation-name: fly-right-one;
	animation-timing-function: linear;
	animation-iteration-count: infinite;
	
	&--one {
		animation-duration: 15s;
		animation-delay: 0;
	}
	
	&--two {
		animation-duration: 16s;
		animation-delay: 1s;
	}
	
	&--three {
		animation-duration: 14.6s;
		animation-delay: 9.5s;
	}
	
	&--four {
		animation-duration: 16s;
		animation-delay: 10.25s;
	}
	
}

@keyframes fly-cycle {
	
	100% {
		background-position: -900px 0;
	}
	
}

@keyframes fly-right-one {
	
	0% {
		transform: scale(0.3) translateX(-10vw);
	}
	
	10% {
		transform: translateY(2vh) translateX(10vw) scale(0.4);
	}
	
	20% {
		transform: translateY(0vh) translateX(30vw) scale(0.5);
	}
	
	30% {
		transform: translateY(4vh) translateX(50vw) scale(0.6);
	}
	
	40% {
		transform: translateY(2vh) translateX(70vw) scale(0.6);
	}
	
	50% {
		transform: translateY(0vh) translateX(90vw) scale(0.6);
	}
	
	60% {
		transform: translateY(0vh) translateX(110vw) scale(0.6);
	}
	
	100% {
		transform: translateY(0vh) translateX(110vw) scale(0.6);
	}
	
}

@keyframes fly-right-two {
	
	0% {
		transform: translateY(-2vh) translateX(-10vw) scale(0.5);
	}
	
	10% {
		transform: translateY(0vh) translateX(10vw) scale(0.4);
	}
	
	20% {
		transform: translateY(-4vh) translateX(30vw) scale(0.6);
	}
	
	30% {
		transform: translateY(1vh) translateX(50vw) scale(0.45);
	}
	
	40% {
		transform: translateY(-2.5vh) translateX(70vw) scale(0.5);
	}
	
	50% {
		transform: translateY(0vh) translateX(90vw) scale(0.45);
	}
	
	51% {
		transform: translateY(0vh) translateX(110vw) scale(0.45);
	}
	
	100% {
		transform: translateY(0vh) translateX(110vw) scale(0.45);
	}
	
}