Starting frame is not set:

Ending frame is not set:

Compare animations

animation-fill-mode: forwards;

animation-fill-mode: backwards;

animation-fill-mode: both;

animation-direction: normal;

animation-direction: reverse;

animation-direction: alternate;

animation-direction: alternate-reverse;

animation-timing-function: ease;

animation-timing-function: ease-in;

animation-timing-function: ease-out;

animation-timing-function: ease-in-out;

animation-timing-function: linear;

animation-timing-function: steps(5, start);

animation-timing-function: steps(5, end);

animation-timing-function: step-start;

animation-timing-function: step-end;

animation-timing-function: cubic-bezier(0, 1.1, 0.8, 4);