What changes at Town Hall 12
Town Hall 12 is the first level where the Town Hall itself fights back: once the Giga Tesla is active, a TH12 layout has to decide whether the Town Hall anchors the core or pulls attackers into a controlled route. Siege Machines also become central to most attacks, so the path a Wall Wrecker, Battle Blimp or Stone Slammer would take is worth checking before you copy a layout.
Compare layouts by Town Hall position first, then by how the Eagle Artillery, Inferno Towers and air defenses are spread. A base that groups every high-value defense near the centre can be strong against ground pushes but easy value for a well-placed Blimp or air spell set.