I was a bit confused at first (because I'm an idiot who skims tutorials), but once I realized how to play the game became very fun very fast. This was a frantic test of how well I can do addition in my head on a timer, and I enjoyed it a lot. For some feedback, I think it would be nice to make the timer a bit more prominent, both in its size on the screen and perhaps some additional ticking sounds when it gets close to zero, since I sometimes found myself getting so locked in on the game I was suprised when the timer went off. Other than that, good work on this submission!

This was so good. I actually had adrenaline pumping racing against the clock. I think I gained few braincells after this.

This was actually pretty creative, when thinking of count down the last thing I think of is card game, nice game!