Cute game! While simple, the visual and audio styles worked well together, though I did miss having some kind of background music.

In addition, having some sort of repeating melody of sounds play as the frog walks (Mario Maker 2's level building tool comes to mind) rather than the monotone "bonk" noise would be a nice addition. It does get a little repetitive.  

I especially like Frog's lopsided face and blank stare. The grave acting as both a respawn point and a shield is a genius bit of versatility, which reminds me of this talk from the creator of Downwell. You took a simple mechanic (moving a block) and made it work for so many different purposes! 

On the other hand, I found the dash/speed boost to be fun, but not particularly useful: I solved  every puzzle in the game without it. Personally I think that the effort spent there would have been better spent on other aspects of the game. (That being said, I've made plenty of "useless" mechanics in my day, just for the fun of it! The dash is fun, so why not have it?!)

There are several puzzles that require you to first place the gravestone in front of a turret, and then later push it away: placing yourself directly in the path of the turret at point blank range. I died quite a few times just trying to push the tombstone away from the turrets, and found it mildly frustrating. Of course, dying right next to the tombstone didn't really affect my ability to complete the puzzle, and ultimately I was just being impatient. I'm not sure what a solution to that would be, though.

Overall, I enjoyed my time with Here Lies Frog, and I think all of my criticisms fall in to "it's a game jam game, so obviously it would be more polished if I had spent more time on it" category. It's got a good, consistent aesthetic, a unique mechanics and some nice puzzles. You should be proud!