C01C: 8E 20 00     LDX #$2000   Set X to address 0x2000
C02B: 6F 80        CLR ,X+      Set memory at X to 0
C02D: 8C 26 F9     CMPX #$26F9  Check if we've reached 0x26F9
C01E: 26 F9        BNE $002B    Keep going if not

This zeroes all the memory between 0x2000 and 0x26F9, a total of 1,785 bytes. Perhaps this is where we'll be storing all of our variables and other data?

Not that it's going to make much difference, but I wonder why we don't set 2 bytes at a time like we did when clearing the screen?

i.e.

LDD #$0000   Load D with 0000
STD ,X++     Store 0000 to memory

instead of CLR ,X+ Clear to memory (i.e. store 00)

Possibly because we're dealing with an odd number of bytes here, so if we set two at a time we need to add another instruction at the end to set just one.

Or maybe the routine when clearing the screen was a copy-and-paste from elsewhere, hence just someone else's coding style.