Battlecruisers is a free RTS battle game from Mecha Weka. A game starts with two sea control ships at either end of the 2d playfield. You start with a few builder drones to build other ship modules, which include more builder modules to get more drones (all modules have a minimum number of drones required to build them, though you can concentrate more drones to build a module faster).

Build drone modules, ship defenses then ship offenses. Offenses include a naval shipyard to build small attack ships (4 types), an aircraft factory for aircraft (3 types), big guns and rockets up to a death star (my favorite) and a nuclear missile (guarantee kill but takes a long time to build). Defenses include anti-ship guns to deal with enemy attack ships, anti-air for enemy aircraft (though the aircraft factory is very versatile as you can build anti-ship, anti-aircraft, and attack aircraft types), shield modules and various specialty modules.

It's an RTS game so you keep switching to the enemy ship to see what he's doing and then counter build (there is a cloak module and a spy satellite module to negate the cloak module). Touch UI is mixed. Three buttons to zoom in on your ship, the enemy ship, and to zoom out to the whole playing field. But after that it gets a bit fiddly if you want to zoom in and out manually and on my iPad the touch points to select mount points are small in default zoom.

There's a campaign of 25 levels with three difficulties. I did Easy which is really easy and I'm doing Normal now which requires much more attention to counter enemy builds but still not had. I expect in Hard the enemy starts out with more builders which makes it hard as you defend while trying to increase your builder drones.

Overall a pretty fun game. Free on iOS (has ads but rather seldom). Also available on Windows ($6).