Originally, GIANT SHOOTY SPACEFLEETS, er, I mean, SUNDER THE STARS was based on the mechanics of MEKA TAC - GIANT STOMPY ROBOTS EDITION. It has since moved beyond that. In an attempt to both speed up and simplify the mechanics, many things had to be altered or eliminated to allow the deployment of fleets on the tabletop, not just a paltry couple of ships per player.
The unopposed "TO HIT" roll followed by a damage roll has been replaced with an opposed roll of Attack Value +/- modifiers + D vs. Defense Value +/- modifiers + D. How well the attacker rolls vs. the defender not only determines if the attack was successful, but how destructive it was. The greater the difference between attacker and defender, the more damaging the result. It also keeps players participating in the game even if they are not currently activating units.
Weapon types have been consolidated and the tracking of ammunition has been removed.
Ships no longer have individual record sheets, but each ship type has one record sheet. This does not mean that all "Light Cruisers (CL)" are identical. If you want different types of CL in your fleet, then you would have a different sheet for each type.
Check boxes have been done away with. The entire ship's offensive and defensive systems degrade as the ship takes damage. Recording damage has been abstracted to rows of stats on each record sheet. An undamaged ship would use the top row of stats. As the individual ship took damage, you would go to the next, less powerful stat row. When sufficiently damaged, the ship would be removed from play. Smaller ships have less damage tracks than larger ships. The current status of each ship - like which damage track to use for that ship - would be recorded by a few counters next to or on the base of the model. If the model's base isn't big enough, the record sheet would have "status lines" where each ship's counters would be placed.
Some of the things that were kept:
Games may be played either on maps or mats with hex grids, or on an open table with terrain.
Ranges and movement may be scaled to fit the size of your models or play area.
Example units (and fleets) will be listed and may be completely ignored as a full set of unit construction rules will be included.
The Action Cards will be included, and remain optional.
Playtesting will be starting in the next few weeks. More information to follow.