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Title-screen renderer

src/graphics/title_screen.asm owns CPU $CBA6-$CD52. It contains a packed direct-PPU renderer, two callers that compose the title/record screen, and the small fixed tile and buffered-update templates consumed by those callers.

Packed stream format

RenderPackedTitleData receives a 16-bit source pointer in TempPointer00. It maintains a logical column in $02 and row in $03 and interprets each nonnegative byte as a cursor command:

Value Meaning
$00-$3F replace the logical column
$40-$5F replace the logical row
$60-$7E add (value & $1F) + 1 to the row
$7F terminate and return
$80-$FF literal tile byte written to PPU_DATA

The extra one in the relative-row command comes from the carry left set by CPX #$60; the decoder deliberately does not clear it before ADC. Literal runs are followed by a positive command. At that boundary the routine advances the base source pointer by Y, resets Y, and interprets the command without losing it.

SetPackedTitlePpuAddress converts the logical row and column into the two PPU address bytes. Its shifts, masks, and rotates carry the row's nametable bits into the high bits of the low address byte, allowing one stream to address the mirrored title layout.

Record/background layer

DrawTitleRecordLayer renders TitleRecordPackedData at USA $CD5F / Europe $CCEF, writes a 21-byte fixed tail in reverse order, then queues static PPU streams $09-$0B. It reuses BuildScoreDisplayUpdate three times with local headers to publish:

  • the current seven-digit score;
  • the seven-digit warm-RAM best score;
  • the two-digit warm-RAM best GDV.

Leading zeroes in the best score become blank tile $24, matching the normal HUD formatter. The best GDV passes through FormatTwoDigitNumberTiles. Each buffered update waits for PpuUpdateStreamPointer to become idle before reusing the shared buffer.

Logo layer

DrawTitleLogoLayer waits for vblank, queues static stream $05, and renders TitleLogoPackedData at USA $CDFA / Europe $CD8A. It then writes three fixed direct-PPU patterns: 16 alternating $DF/$DE pairs, eight $F5 tiles, one $CF accent, and a seven-byte attribute sequence.

Both packed streams are source-owned in PRG_TITLE_PACKED_DATA. The first is 155 bytes and ends at $CDF9; the second is 247 bytes and ends at $CEF0. Each includes its $7F terminator, and assembly assertions preserve their exact adjacency and sizes.

make title-data-audit independently decodes the two streams into semantic cursor commands and literal runs, reproduces the carry-dependent PPU address calculation, and re-encodes all 402 bytes. The reviewed manifest records 25 commands, 17 literal runs, 377 literal tiles, exact boundaries, and SHA-1 fingerprints in config/validation/title_data.json. make title-data-report exposes the decoded commands, target PPU addresses, and tiles as JSON.

The same adjacent-data audit includes the attract demo's 34 duration and controller bytes at $CEF1-$CF34. Controller masks are decoded to named NES buttons before re-encoding; see docs/attract_demo_flow.md for playback semantics.

The European layout moves both packed streams and the demo tables $70 bytes earlier: title data occupies $CCEF-$CE80 and demo input occupies $CE81-$CEC4. Their hashes and decoded records are identical to USA. The separate config/validation/title_data_europe.json manifest makes that conclusion an independent ROM-backed contract. make title-data-profile-audits round-trips all 470 bytes from both source-built images.