Trial will continue at 10am on Wednesday
Justice Yip asks for the jury to return at 10am on Wednesday.
The cross-examination of Girl X was concluded today and the case for Boy Y is set to begin tomorrow.
Girl X admitted she liked the idea of causing pain and suffering to Brianna but denied turning her fantasy into reality.
The court heard Boy Y had "gradually stopped speaking" to anyone apart from his mother following his arrest and had been diagnosed with selective mutism, as well as autism spectrum disorder.
He is due to give evidence on Wednesday by typing, the jury was told.
Giving evidence for a second day, Girl X was asked what she enjoyed about the idea of killing.
She said: "I'm not exactly sure, I just found the overall thing quite interesting I guess."
Deanna Heer KC, prosecuting, asked: "Did you find the idea of killing Brianna, who you were attracted to, exciting?"
Girl X said: "I guess so, yes."
The jury heard Girl X had saved Boy Y's phone number in her phone under the name "Tesco John Wick" and that John Wick was a character from a film about a hitman played by Keanu Reeves.