If you are wondering on how to make a TATE mode for your SHMUP in Construct 3, here's the code!
+ System: On start of layout
+ OR Keyboard: On H pressed
-> System: Set canvas size to 640 x 480 (original canvas size is 480 x 640)
-> System: Set layout angle to 90 (change this to 180 and 270 for other Tate Options)
-> System: Set layout scale to 1
This code assumes that you originally built your SHMUP or Vertical Screen game on a Portrait layout with a 3:4 ratio canvas (for example, 480 x 640).
NOTE: I have tiled backgrounds that repeat/loop in my SHMUP, rather than a large scrolling level, so I have no idea if this works in that situation.
Hope this helps any body who is making a SHMUP and wants to create a TATE mode for the absolute savages on the SHMUP forums :)