What does 迷路の奥のダイヤ mean?


Found it in the lyrics of [BUMP OF CHICKEN -
Answer](https://lyricsjpop.blogspot.com.au/2016/12/bump-of-chicken-
answer.html)

> 想像つかない昨日を越えて その延長の明日を抱えて  
>  小さな肩 震える今 それでも笑った  
>  **迷路の奥のダイヤ** のような  
>  届かなかった風船のような  
>  気づけなかった流星のような  
>  涙をもらった

I googled a lot without a clue finally. Is it a reference of a game or
something?




Having read the entire lyrics, I would say that that part is saying:

"Your tears are as precious as a diamond (hidden) in the inner part of a
labyrinth".

(As a non-game-player, I could not answer the game reference bit. I can,
however, say that at least there is no such suggestion made in the lyrics.)

