Responsive Countdown with HTML/CSS/JavaScript

What are you most proud of, and what would you do differently next time?

The flip effect is the most challenging part which I could achieve to complete. The effect is not perfect though, and requires more work to look more realistic.

What challenges did you encounter, and how did you overcome them?

I spent quite a while to create the flip effect. Among the challenges, how to get the other side of the card to show up when it flips and also how to get correct numbers to show up after each flip. Also when flipping, you need some way to hide the back half, i used a div and whenever flip starts i make this div visible and it will become invisible when rotation is complete.

What specific areas of your project would you like help with?

I think the flipping part, as i spent the most time on this part.