ArrDun by Tring
Rules:

@ ➔ ⇨ ⟹ @ 16 ➔ 15

@ ➔ ⇦ ⟹ ✗

@ ➔ ⇧ ⟹ @ ⇧

@ ➔ * ⟹ @ *

@ ➔ * ┃ ⟹ ✗

@ ➔ * * ⟹ ✗

16 ➔ 0 ⟹ 👍