You can set a specific time goal for a session and select a quiz style from "Self-Grading," "Multiple Choice," or the fast versions of those two, which are in a scrolling format and save time from not having to transition between screens. Other than focusing on speed, Hammer has a feature called "Audio Stream," which generates audio for vocabulary items you've learned and their English translations. This is very handy for reviewing vocabulary for busy people as it lets you to multi-task.
The premade flashcard decks are based on the most useful Japanese vocabulary. There's no community-based deck library like on Anki, but you can create your own deck. If you are a complete beginner, read their How To Learn Japanese guide so that you know what you're about to study on Hammer, as well as get some other Japanese learning tips. Hammer has some fun gamification elements like earning coins and collecting badges for you to keep going as well.