Some interesting deets in this twitter thread too:
https://twitter.com/finalfantasyvii/...27600810201088

Difficulties:
Easy, Hard

Combat:
Standard (ATB gauge filled by doing standard attacks)
Classic (ATB gauge fills automatically - designed for those who just want to select commands and ignore the action-combat of Standard)

Summons:
Each character can equip 1 summon materia
Summons have a timer and stay on the battlefield attacking until the timer runs out, once the timer runs out they cast their traditional ability (i.e. Hellfire, Diamond Dust etc.) and leave the battlefield.

Abilities:
Aerith's Triangle ability is called Tempest, it puts an AoE on the ground and any spell cast within that AoE is then cast repeatedly.