Current instant messenger applications are not made to hold a conversation with more than one person. If they have the ability of group chating they show your messages in the right and all the other people messages merged in the left. Then it becomes difficult to know who are the active members of a chat or to read someone's last message.
Even when holding simultaneous conversations (grouped or one-to-one), it is not possible to swap between them without going back to a list of contacts.
ChatStrum is a 2D chat, with the users shown vertically in the screen, and messages timeline horizontally. It is possible to chat with many users in the same screen without the need to go back to the list of users to alternate between chats. Never get lost with merged chats, just double tap on someone's picture and the chat will scroll to that person last messages.
ChatStrum also provides the feature of drawing to express ideas that can't be texted