Tutorial: crisp wave rows

- Pixels tinted by the green filler take the nearest clean pixel's colour and
  keep their own coverage (the neighbourhood average smeared the joints)
- The background layers are drawn at whole pixels: between pixels, filtering
  softened them and darkened their edges

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Scripts/background/bg_collabs/tutorial.lua

@@ -37,12 +37,17 @@ local function at(track, list, f, n)
     return track[list][(f % n) + 1]
 end
 
+-- whole pixels: drawn between pixels, the filtered layers came out soft
+local function px(v)
+    return math.floor(v + 0.5)
+end
+
 -- a strip whose x / y follow its track; rows above the top band are cut off
 function TutorialBackground:strip(name, track_name, f)
     local tr = TRACKS[track_name]
-    local x = at(tr, "x", f, tr.n)
+    local x = px(at(tr, "x", f, tr.n))
     local y = name == "pat" and 0 or (name == "mtn" and 0 or at(tr, "y", f, 120))
-    local top = y + L[name].ytop
+    local top = px(y + L[name].ytop)
     local cut = math.max(0, BAND_TOP - top)
     tex.draw_texture(self.id[name], {
         x = x, y = top + cut, y2 = -cut,
@@ -70,7 +75,7 @@ function TutorialBackground:draw_back()
     local cx = at(TRACKS.cloud, "x", f, TRACKS.cloud.n)
     local cy = at(TRACKS.c9, "y", f, 120) - CLOUD_Y0
     for k = 0, CLOUD_COUNT - 1 do
-        tex.draw_texture(self.id.cloud, { x = cx + CLOUD_X0 + CLOUD_PITCH * k + L.cloud.dx, y = cy + L.cloud.dy })
+        tex.draw_texture(self.id.cloud, { x = px(cx + CLOUD_X0 + CLOUD_PITCH * k + L.cloud.dx), y = px(cy + L.cloud.dy) })
     end
     self:strip("w13", "w13", f)
     self:strip("w16", "w16", f)

checksums.sha256

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 8bcf5446e8bee1b1e13e7778a875b27771d736b55bc616434e7bc9668f504084 *./Graphics/song_select/box/box_chara/10.png
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 7a438cb70361275daed4356d23a504ab38d4ac105bf09bd8c1db0e0577dce775 *./Sounds/game/tutorial/balloon.ogg