Referential clues are a single-card focus convention where a clue tells one card to play or discard, and that card is not generally one of the cards touched by the clue. If a card is told to play, it is called a referential play clue, and if a card is told to discard, it is called a referential discard clue.
Trash pushes are a form of trash tech where touching known trash promises a play of another card. Usually, the card told to play is the untouched card immediately to the left of the focus.
Universal rank saves are more explicitly about saving cards and not providing discard instructions, so they may not count as a form of referential clueing. That said, they deserve a shoutout.
To discuss referential clues it is useful to distinguish between the focus of the clue and the target of the clue. When clues are direct, the same card is both the focus and the target.
For example, one common convention direct discard oldest sytems us is chop focus. The focus priority in these systems is
The target is same as the focus: the card the clue is talking about the important one touched.
On the other hand, in Turbo, Mirror play clues focus the rightmost card introduced by the clue and target the card that the focus mirrors to through unestablished cards.
In other words, the focus priority for mirror clues is right to left, and the target priority is left to right. It can be helpful to identify a focus and target prioirity in order to design a referential clue convention, since once these are determined the clues can often be thought of as following an algorithm: