Caroline Trotdock wrote:I need help learning how to lower walls when crossing over a linedef
That depends greatly on the mapping format you are using.
For original DOOM
select the triggering linedef, to edit it, and open the Floor category
Scan through the list for anything W1 (walkover once) and find a linedef special which lowers the floor.
Select the one which comes closest to want you want to happen. For example:
Note that the floor sector and the linedef special must reference the same sector tag.
, both DiHF and UDMF, you have many more options
For example: Select a linedef to lower the floor in one go or lower the floor incrementally
or lower the floor instantly or at a slower rate, etc.
As before, note that the floor sector and the linedef special must reference the same sector tag.
Or you could elect to use a script (ACS or ZSCRIPT) to have one or more actions take place.
Several things to consider: