We ran a quick game of Grimdark Firefight yesterday evening after work.
Very simple stuff, every unit except the leaders were Q4 D5 with an A1 normal rifle, but with the Advanced Actions special rule.
We played a scenario encounter, with 2 players against a GM and a simple objective (grab the 5 objective markers and don't lose more than 5 dudes in the process).
It was a load of fun, especially finally getting to use these terrains I have been building since forever.
However, I found the lack of reaction rules (beyond the "Overwatch" action) a bit jarring.
It feels like shooting back when being shot at, or being able to interrupt the movement of a unit if it passes through your line of sight should be closer to the default rather than something that costs a full action.
Is there a miniature-agnostic game which is a bit more built around reactions? From what I've seen, Blkout seems to fit the bill pretty well, if it didn't come with pre-built setting and units