diff --git a/2025/day12.ua b/2025/day12.ua
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+~ "aoc.ua" ~ Lines Sections Words
+
+Sections &fras "input/day12.txt"
+
+~Present {Id Shape}
+
+ParsePresent ← (
+  Lines
+  ⋕°$"_:" °⊂
+  ⊙(=@# ≡°□)
+  Present
+)
+
+~Region {W H Req}
+
+ParseRegion ← (
+  °$"_x_: _"
+  ⊙⊙(Words)
+  ∩₃⋕
+  Region
+)
+
+⊃(≡◇ParsePresent ↘¯1|≡◇ParseRegion Lines°□⊣)
+
+⍤"3x3 bounding box" ≍ ¤[3 3] ◴⊸≡(△Present~Shape)
+
+⊃(⋅∘|∘)
+
+# bool ? Region Presents
+Impossible ← (
+  ×⊸⊃(Region~W|Region~H)
+  ⊙⊓(Region~Req|≡(/+♭ Present~Shape))
+  ⊙(/+×)
+  >
+)
+
+# int ? Width Height
+Blocks ← ×∩(⌊÷3)
+
+# bool ? Region
+Guaranteed ← (
+  Blocks⊸⊃(Region~W|Region~H)
+  ⊙(/+ Region~Req)
+  ≤
+)
+
+⊃(≡⌟Impossible|≡Guaranteed)
+
+⍤"no searching required" ≍ [1] ◴◡+
+
+◌
+/+