It simply relpaces rulers with squares to measure movement and weapon ranges. The squares also regulate unit position. It's a bit like playing a board game with miniatures.
In theory the downside is a loss of "fidelity" in unit position and distances. Tradtional ruler-based games are ** CENSORED ** (that would be a--n--a--l--o--g...so much for automated naughty word control!) sort of like old LPs while square or hex based games are "digital" like CDs. With rulers you get virtually infinite degrees of unit position, distance, and angles while with squares/hexes you get measurements and postions in chunks as large as the square/hex.
The advantage is speed of play since distances and position have a much higher degree of certainty. An extreme example is DBM in ancients wargaming which can be dominated by arguements over a mm or two and some moderns games in which a tiny difference in shot angle can mean the difference between oblivion and a ringing rickochet! With squares these tiny measurement and angle issues disappear. And common actions such as moving stands are much faster since they require the simple counting of squares.
In my experimental rules (and PBI) a square can contain a number of stands before being considered "over crowded" and subject to penalties which make it easier to score hits against targets in the square. In my rules this is 4 stands in a 10cm x 10cm square (ie over 4 stands and the shooter gets a +1 to hit for each stand over 4).
LOS is determined by drawing a line from shooter's square center to target's square center...if a square with buildings or woods clips this line LOS is blocked. The position of a stand within a square is immaterial (avoids lots of tradtional "discussions" as to tiny differences in angle, range, etc.) but vehicles/towed weapons must face one of the 8 possible directions in a square.
Move distances, weapon ranges, and other distance-related rules are given in squares (eg command and control distances). Terrain is also square based so that each square is considered to be a specific terrain type. Counterintuitively this does not result in a blocky terrain presentation since while the game mechanics are square-based the terrain within a square can have very natural visual curves (eg a woodline or area of broken terrain).
Also counterintuitively it's very, very easy to mark a cloth in squares. With a tape measure simply mark dots at 10cm / 4" intervals along one side of a cloth. Do the same on the opposite side. Then placing the tape across the cloth and "level" with dots on opposite sides simply mark dots at 10cm / 4" intervals across the cloth and work your way down. Perfection is not required but getting pretty close to prefection is very easy and fast (about 20 minutes for a 4' x 6' cloth).
Microarmor, even when mounted on stands, is very lightwieght and easily displaced accidently (especially when placed on top of terrain features!) I really like combined arms games which means tanks AND infantry and the infantry stands are REALLY lightweight. In other periods and scales units are usually large enough, heavy enough, and dense enough that "incidental movement" and minor differences in distances and angles are not as much of an issue. But with tiny 1" x 1" microarmor stands the squares seem to mitigate the problems associated with minitaures that can be so easily (and significantly!) displaced by a tiny variation in model terrain, a table bump, or unsteady wargamer!
I've tried this before but didn't see a big a benefit with larger scales. But with microarmor there seems to be a very significant ergonomic benefit that makes gaming far more enjoyable and trouble free.
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