Board Thread:News and Events/@comment-26005122-20180308041852/@comment-26005122-20180308231709

Each of the four ships is a mission. If it says "クリア済" over the ship, it means the mission was cleared, possibly by one of your Friends who played your mission. You can play other people's missions to earn support points. If you press the yellow bar between the left arrow and the pause buttons, you can see which friends have been supporting you and helping you clear your missions.

On the ranking screen, where the Heart Icon usually is, you'll see either, Star Command, an Alien, or Zurg. You can help your friends with their missions, rescue Aliens, or fight Zurg, depending on the icon.

The middle ship shows up when you clear all 4 ships. That is the Star Command space station. Story-wise, you report to Star command about the missions from the other ships, and it rewards you with points.