.slide { display: none; margin-bottom: 20px; }
.slide:not(.hidden) { display: block; }
.hidden { display: none; }
.feedback { margin-top: 10px; font-style: italic; color: #2a2; }
.timer { height: 5px; background: #0a0; width: 0%; animation: grow 5s linear forwards; margin-top: 5px; }
@keyframes grow { from { width: 0%; } to { width: 100%; } }