This tutorial is a guide on how to modify the status bar (and a little bit of using the overworld border). It also includes various custom subroutines and sample codes on how to use them.
-A patch DefaultTiles.asm that modifies the status bar and hardcoded tiles in a user-friendly way.
-32-bit HexDec (ideal for big currency system)
-RepeatedSymbols (display how many n items out of x)
-left/right-aligned number display (removes leading zeroes instead of replacing them with leading spaces)
-Leading zeroes remover
-32-bit frame counter to timer display