The heart symbol under a character's health fills up during the match, then gives you a stock when full. The 4 stock levels are 1, 2, 3, and MAX. As it fills, your Bride Attacks will power up. Bursts cost one stock. When you lose a round, you will gain a stock at the beginning of the next.
The blue bar at the bottom of the HUD is tied to your Bride. It depletes when using Bride Attacks, Boosts, and Bride Reflects. Once emptied, there is a cooldown period.
The green bar underneath the Bride Meter is your standard fighting game super meter. It can be used for EX Moves, Bride Counters, and supers when full.
Boosts are the crux of your movement in Daemon Bride. They can be done on the ground or in the air with any direction and the D button. Boosting lets you move around in the air and go through projectiles. It depletes the Bride Meter.
Pressing D when knocked down lets you recover faster with a Boost. Like Boosting, it depletes the Bride Meter.
By pressing BC while blocking, you can push away the opponent and make room. This depletes the Bride Meter.
Pressing ABC in hitstun will let you burst out and enable counterattacks. This depletes the Bride Meter faster than other systems.
Pressing 6AB while blocking will let you get out of pressure and counterattack. This costs one Force Meter stock.
All of your physical specials can be enhanced when done with AB. This costs one Force Meter stock.
If you are in the final round, have less than 20% health, and have three stocks of Engagement Meter, pressing ABC will let you enter Climax. Damage and Force Meter gain is increased in this state. You can do your super without having a full bar in this state, and it will be enhanced. Doing so will end Climax.
Throws are 4F startup. They behave similarly to Arcana Heart:
5A+D/6A+D/Front Throw launches them into the air for a combo followup
4A+D forces a knockdown and a sideswap
This also means that you can punish air techs with throw! (Example)