where did my math took wrong turn?

[vocal cloak]

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[balmy pendant]

Don't use single comments like that ever in macros

Use a multiline comment /* */ if you must use a comment inside a macro

Basically what happens is SCREEN_WIDTH expands like this:

1. SCREEN_WIDTH
2. DISPLAY_WIDTH  * DISPLAY_SCALE // 640
3. TILE_SIZE * TILE_ROW_LEN // 256 * DISPLAY_SCALE // 640
```And hopefully here you see the issue

[indigo pecan]

Wot, that's not how it works.

[balmy pendant]

Am I misremembering?

[indigo pecan]

You are.

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[balmy pendant]

Oh, I'm thinking of multiline macros with \