Talk:Spring 2015 Event/@comment-114.121.156.254-20150427104555/@comment-25730832-20150427110048

To make you suffer even more. From the description in the Recent update page:
 * Ship-locking confirmed for Medium & Hard Mode[6]
 * Ships used in E-3 can't be used in E-4
 * Ships used in E-3 & E-4 can't be used in E-5
 * You can freely deploy ships to a map if you select Easy Mode for it
 * E-6 has no ship-locking whatsoever, so you can use all ships regardless of the difficulty setting.[7]

So whatever you used in E-3 can be used in E-4 or E-5, and vice versa. The point isn't E-6 ignores all locks; it's "can you survive long enough to reach E-6 with 3 ship locks (E-3, E-4 and E-5) blocking your way. There's no other purpose than making you suffer more.

Or you can just do easy.