Enemy ships move IMMEDIATELY AFTER PLACING A DIE. You can't place all five dice first and then move the ships, because they often change columns. So you place a die, move all ships in its column, place another die, move ships in that column, etc.
All ships in a column MOVE SIMULTANEOUSLY. So there can be no collisions.
Ships trigger only the effect of a space where they END their movement. Ignore spaces they passed through.
The effects of spaces are resolved after all ships in that column have moved and they are RESOLVED FROM THE TOP. This can be important when more ships end their movement on a mothership icon.
When a WHITE ship hits the city, it RETURNS TO THE MOTHERSHIP to be respawned in the Mothership Phase. So in this matter, it behaves the same as a purple ship. It is removed only after being shot down.
Descending the mothership
When a ship ends its movement on a MOTHERSHIP ICON, the mothership descends one row. But in this case, it DOES NOT TRIGGER THE EFFECT of that row.
When there are any ships in the row below the mothership when it should descend, those ships are returned to the mothership. However, they are NOT IMMEDIATELY RESPAWNED. They are placed on the mothership tile (without being assigned to drop points) to be respawned in the Spawning Ships step of the Mothership Phase.
Excavator
It costs ONLY 1 ENERGY to move the excavator, regardless the number of spaces it moves.
The value of a die placed for excavating needs to be THE SAME OR HIGHER than the distance from the excavator. In other words, to move the excavator 4 spaces, you need to place a 4, 5 or 6 value die four spaces in front of the excavator. It's NOT possible to place a lower value die and increase it later by some effect.
A die used for excavating does NOT activate the room where you've placed it.
When counting the number of spaces to move the excavator, don't forget to COUNT THE TUNNELS and remember that MULTI-SPACE ROOMS count as multiple spaces. Each level of the base consists of 5 spaces.
The excavator moves during the Rooms Phase, so you usually can't use the newly excavated rooms in the round you excavate them. However, since you can resolve dice in the Rooms Phase in any order, you can move the excavator first and then activate a robot room to install a robot in one of the newly excavated rooms.
Activating rooms
You can decide NOT TO USE a room to save energy. In that case, simply remove the die in the Rooms Phase with no effect. While you can place a die on a tunnel if you want to move a ship by a full value, it's usualy better to place that die on a room and later decide whether to use it or not.
Shooting down enemy ships
A jet fighter room targets ALL SHIPS on explosions, not only those in the room's column.
To shoot down a ship, the value of the jet fighter room needs to be THE SAME OR HIGHER than the number on the explosion.
White ships DON'T RESPAWN after being shot down.
Researching
You CAN'T ADD ROOM VALUES together. So to advance to the last space of the research track, you need to use some of those double or triple research rooms.
You can advance MORE SPACES at once, if the value of the research room is the same or higher as their sum.
Robots
Robot dice DO NOT MOVE SHIPS in any way, not when being installed and neither when being activated.
Robots DECREASE ONLY AFTER BEING USED. When you decide not to use a robot in a round, it retains its value.
You can remove a robot AT ANY TIME. It can be useful if you really need to use its room with a higher value.
You can't usually move a robot to a different room. To do that, you would need to remove it and install a new one by activating a robot room.
A robot CAN BE INSTALLED IN A ROBOT ROOM, even in the same room that created it. When activating a robot room containing a robot die, you can even use that die as the newly installed robot.
Respawning ships
Ships respawn only in the Mothership Phase. So when a ship hits the city, if a mothership descends to a row containing a ship, or if you shoot down a ship, they are placed on the mothership tile, but they are not assigned to drop points until the Spawning Ships step of the Mothership Phase.
Ships don't automatically respawn in the same column where they've been shot down. See the Spawning Ships on page 9 in the rulebook.
Respawned ships are placed on drop points (those ship-shaped semi-transparent spaces on the mothership tile) and not in the row below the mothership tile.
It can happen that a ship doesn't leave a drop point (usually when placing a value 1 die in an AA gun room). In that case, when the mothership descends, the ship stays on that drop point and moves with the mothership. Also, for the sake of respawning ships, a ship occupying a drop point does not mix with the other ships waiting for the respawn. It simply remains on its drop point.