This game involves a lot of mousing over characters/enemies ("figures"). But apparently they've implemented this basic hover detection very poorly, because the game can only do it (appears to be GPU-bound spikes) at about half your normal refresh rate.
The game jerks badly when you're moving the camera such that the mouse cursor hits any characters/objects.
Given my normal smooth refresh rate is 75 Hz, that means the smoothest gameplay I can get is a little over 30 FPS, steady.
Hope you're playing on an old blurry LCD to hide those afterimages.
It's a shame that a dumb coding AKA logic mistake ruins and otherwise fluid experience.
This is a changelog where they mention "optimizing" this hex highlight: https://steamcommunity.com/app/780290/discussions/0/1643169167151064379/#c1642045003579072193 Maybe they should pay attention to character hover, too.