our level 2 base had 3 disruptor turrets +400 attack thought I would upgrade to the Singularity Turret +800 ....sold the lesser then couldn't build the bigger guns till lvl3 ....... wish it had had a "tooltip" to inform me that before I had sold the lil guns.... just a thought

Are you sure it doesn't? When I hover over the "Build" button for higher level things it says we can't build them until level 4 or 5.

If you don't have enough space it just tells you you don't have enough space. If you DO have enough space it will tell you you don't have the required level yet.

Ah, one of those cases. Yeah, it'd be nice if "not enough space" had lowest priority.

no prior to selling lil guns the tool tip says (not enough space) so sold lil guns then when I went to build is when it informed me (must reach lvl3)