2500 distance is quite hard. I manage to get 2000+ every run, but didn't reach the 2500 once. Gauss rifle and shark gun seem to be the best guns to pick and the remote control is great too.
I guess it's a fun game nevertheless!
It seems I can't block any attacks.
I tried the "on the brink" challenge plenty of times, but I lose it every single time. I tried different card decks, but my best score so far is getting the enemy down to 20 life. It seems you should have at least a few healing cards you.
Overall, it's an easy and fun game!
Thanks Jordyman31!