phoenix200689,
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<!-- <link rel="stylesheet" href="style.css"> -->
</head>
<body>
<div class="fixed-wrap fixed-wrap__modal">
<div class="modal">
<div class="modal-container">
</div>
</div>
</div>
<button class="tasks__btn" type="submit">+ добавить задачу</button>
<style>
.fixed-wrap {
display: none;
position: fixed;
overflow: auto;
left: 0;
top: 0;
width: 100%;
height: 100%;
background: rgba(0, 0, 0, .6);
opacity: 0;
transition: opacity 1s;
}
.fixed-wrap._show {
opacity: 1;
}
.tasks__btn {
cursor: pointer;
}
</style>
<script>
document.addEventListener("DOMContentLoaded", function() {
document.querySelector(".tasks__btn").addEventListener("click", function() {
var popup = document.querySelector(".fixed-wrap");
popup.style.display = "block";
window.setTimeout(function() {
popup.classList.add("_show")
}, 0)
})
});
</script>
</body>
</html>