I thought it runs very smoothly.
I thought a bit more clarity on what controls do what would be good.
First time playing, I just walked around while the rocks were crashing down upon me, and I thought, "Oh, I guess I just have to avoid them." Then, "GAME OVER" appeared and I was like, "WTF?"
So even a screen for, "Controls" or introducing them would be nice.
I figured it out eventually that it IS the A button.
And now I see that in the "author's comments" but put them in the game as well!!
Other than that, very smoothly played, great action, overall, very well done for your first game!