diff --git a/day09.py b/day09.py
new file mode 100644
index 0000000..7a9743e
--- /dev/null
+++ b/day09.py
@@ -0,0 +1,85 @@
+from itertools import combinations
+from tools.aoc import AOCDay
+from tools.coordinate import Polygon, Coordinate, Line
+from typing import Any
+
+
+
+class Day(AOCDay):
+    inputs = [
+        [
+            (50, "input9_test"),
+            (4745816424, "input9_dennis"),
+            (4737096935, "input9"),
+        ],
+        [
+            (24, "input9_test"),
+            (1351617690, "input9_dennis"),
+            (1644094530, "input9"),
+        ]
+    ]
+
+    def part1(self) -> Any:
+        tiles = [tuple(map(int, line.split(","))) for line in self.getInput()]
+
+        ans = 0
+        for pair in combinations(tiles, 2):
+            area = (abs(pair[0][0] - pair[1][0]) + 1) * (abs(pair[0][1] - pair[1][1]) + 1)
+            if area > ans:
+                ans = area
+
+        return ans
+
+    def part2(self) -> Any:
+        tiles: list[Coordinate] = [Coordinate(*map(int, line.split(","))) for line in self.getInput()]
+        p = Polygon(tiles)
+
+        ans = 0
+        decomposed = list(p.decompose())
+        for pair in combinations(tiles, 2):
+            found_tile_inside = False
+            for x in tiles:
+                if min(pair[0][0], pair[1][0]) < x[0] < max(pair[0][0], pair[1][0]) and min(pair[0][1], pair[1][1]) < x[1] < max(pair[0][1], pair[1][1]):
+                    #print("IGNORE", other_corner, last_tile, tile, "=>", x)
+                    found_tile_inside = True
+                    break
+
+            if found_tile_inside:
+                continue
+
+
+            found_tile_outside = False
+            for c in [Coordinate(pair[0][0], pair[0][1]), Coordinate(pair[1][0], pair[1][1]), Coordinate(pair[0][0], pair[1][1]), Coordinate(pair[1][0], pair[0][1])]:
+                found_tile_inside = False
+                for r in decomposed:
+                    if c in r:
+                        found_tile_inside = True
+
+                if not found_tile_inside:
+                    found_tile_outside = True
+            if found_tile_outside:
+                continue
+
+
+            found_intersection = False
+            p_line = Line(pair[0], pair[1])
+            for l in p.lines:
+                if l.start in pair or l.end in pair:
+                    continue
+                if l.intersects(p_line):
+                    found_intersection = True
+                    break
+
+            if found_intersection:
+                continue
+
+            area = (abs(pair[0][0] - pair[1][0]) + 1) * (abs(pair[0][1] - pair[1][1]) + 1)
+            if area > ans:
+                ans = area
+
+        return ans
+
+
+if __name__ == '__main__':
+    day = Day(2025, 9)
+    day.run(verbose=True)
diff --git a/inputs/input9 b/inputs/input9
new file mode 100644
index 0000000..8bfa406
--- /dev/null
+++ b/inputs/input9
@@ -0,0 +1,496 @@
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diff --git a/inputs/input9_dennis b/inputs/input9_dennis
new file mode 100644
index 0000000..53648d5
--- /dev/null
+++ b/inputs/input9_dennis
@@ -0,0 +1,496 @@
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\ No newline at end of file
diff --git a/inputs/input9_test b/inputs/input9_test
new file mode 100644
index 0000000..7fb70de
--- /dev/null
+++ b/inputs/input9_test
@@ -0,0 +1,8 @@
+7,1
+11,1
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+7,3
\ No newline at end of file