Doors
The major change is the introduction of doors as a concept. Previously, crew could pass between any two adjacent tiles, even if that meant hovering through the ceiling or walking through the air between two only somewhat adjacent ladders.
With this change, each kind of module now has a known set of doors. A fire point, for example, which is a 2x2 tile module, only has a door at the bottom left and on the bottom right. A coal store has a door at the bottom left and right, as well as a ladder going up to a hatch at the top right. Corridors all have ladders leading up to hatches and can hence act as a connective "glue" for the ships.
Previously, it was not always very clear why you could not place a particular module in the editor. With defined doors, this becomes a lot clearer. An added benefit is that it makes ship layout more interesting - you no longer can put two modules on top of one another and just expect them to be connected.
Pre-combat Layout
Until now, when you set up a fight - either versus the computer or multiplayer - you just chose the list of ships you wanted in your fleet, and the game would arrange them for you. I've now introduced a layout system that lets you place your fleet in the desired formation before the start of battle, which makes things a lot better, and also gets rid of problems like ships spawning above their service ceiling and crashing into others below them!
Ship Pricing
Airship modules and armour now have prices, which lets you set a maximum fleet cost in multiplayer. Pretty important, since multiplayer fights will be all about making the best designs for the least cost, and making the best use of them.
Buildings
OK, buildings are pretty much just airships that can't fly. Still, it's useful to distinguish the two to, for example, make it clear that buildings should never spawn in midair.
New Modules and Armour
There's a huge number of modules still to be implemented later, but for purposes of balance, I have added a few now:
Fire extinguishers act much like normal corridors, but contain a small reserve of water to put out nearby fires. Very handy if you don't have space for a full fire point.
Rockets do large amounts of damage and are especially effective against wooden targets. On the minus side, they are very inaccurate, consume a lot of ammo and explode quite easily.
Grenades also do a lot of damage against wooden targets and enemy sailors, but have a restricted range, so you have to move in close to use them.
Additionally, there's now stone "armour", which is very heavy compared to wood and steel, but can absorb a lot of damage before breaking.
Next up? I've been thinking about project risks and how to release the game, and of course, it's time for the campaign!