Blades in the Dark has a structure to play, with four parts. By default, the game is in free play—characters talk to each other, they go places, they do things, they make rolls as needed.

When the group is ready, they choose a target for their next operation, then choose a type of plan to employ. This triggers the engagement roll (which establishes the situation as the operation starts) and then the game shifts into the score phase.

During the score, the PCs engage the target—they make rolls, overcome obstacles, call for flashbacks, and complete the operation (successfully or not). When the score is finished, the game shifts into the downtime phase.

During the downtime phase, the GM engages the systems for payoff, heat, and entanglements, to determine all the fallout from the score. Then the PCs each get their downtime activities, such as indulging their vice to remove stress or working on a long-term project. When all the downtime activities are complete, the game returns to free play and the cycle starts over again.

The phases are a conceptual model to help you organize the game. They're not meant to be rigid structures that restrict your options (this is why they're presented as amorphous blobs of ink without hard edges). Think of the phases as a menu of options to fit whatever it is you're trying to accomplish in play. Each phase suits a different goal.