diff --git a/2025/09.rs b/2025/09.rs
index 8397215..d1a2249 100644
--- a/2025/09.rs
+++ b/2025/09.rs
@@ -1,8 +1,26 @@
 ---cargo
+[profile.dev]
+opt-level = 3
+
+[dependencies]
+rayon = "1"
 ---
 
+use rayon::prelude::*;
+
 static CONTENT: &'static str = include_str!("./inputs/09_1.txt");
 
+const PRINT: bool = false;
+
+#[derive(Debug, PartialEq, Clone, Copy)]
+enum Cell {
+    Empty,
+    Red,
+    Green,
+}
+
+const _T: () = assert!(1 == core::mem::size_of::<Cell>());
+
 fn main() {
     let points: Vec<(usize, usize)> = CONTENT.lines().map(|l| l.trim()).filter(|l| !l.is_empty()).map(|l| {
         let (first, second) = l.split_once(',').unwrap();
@@ -12,17 +30,124 @@ fn main() {
 
         (first, second)
     }).collect();
-    println!("Points:\n{:?}", points);
+    // println!("Points:\n{:?}", points);
 
-    let mut rects: Vec<((usize, usize), (usize, usize), usize)> = points.iter()
-        .flat_map(|p| core::iter::repeat(*p).zip(points.iter().copied()))
+    let grid_width: usize = points.iter().map(|(x, _)| *x).max().unwrap()+1;
+    let grid_height: usize = points.iter().map(|(y, _)| *y).max().unwrap()+1;
+
+    let mut grid = vec![Cell::Empty;grid_width*grid_height];
+    for parts in points.windows(2).chain(core::iter::once(&[points.last().copied().unwrap(), points.first().copied().unwrap()] as &[(usize, usize)])) {
+        let start = parts[0];
+        let end = parts[1];
+
+        let g_points = line_point_iter(start, end);
+
+        grid[start.1 *grid_width+ start.0] = Cell::Red;
+        for (x,y) in g_points {
+            grid[y*grid_width+x] = Cell::Green;
+        }
+    }
+    print_grid(&grid, grid_width, grid_height);
+
+    let inner_point = points.windows(2)
+        .filter(|p| {
+            let start = p[0];
+            let end = p[1];
+
+            start.0 == end.0
+        }).filter_map(|p| {
+            let start = p[0];
+            let end = p[1];
+
+            line_point_iter(start, end).next()
+        }).flat_map(|(x, y)| {
+            [(x-1, y), (x+1, y)]
+        }).filter(|(x, y)| {
+            (0..grid_width).contains(x)
+        }).find(|(x, y)| {
+            let c = (0..*x).map(|x| grid[y*grid_width + x]).filter(|c| *c == Cell::Green).count();
+
+            c == 1
+        }).unwrap();
+
+
+    println!("After filling");
+    print_grid(&grid, grid_width, grid_height);
+
+    let largest = points.par_iter()
+        .flat_map_iter(|p| core::iter::repeat(*p).zip(points.iter().copied()))
         .filter(|(f, s)| f != s)
         .map(|(f, s)| (f, s, (f.0.abs_diff(s.0)+1) * (f.1.abs_diff(s.1)+1)))
-        .collect();
+        .filter(|(f, s, _)| {
+            let x0 = f.0.min(s.0);
+            let x1 = f.0.max(s.0);
 
-    rects.sort_by_key(|(_, _, a)| *a);
+            let y0 = f.1.min(s.1);
+            let y1 = f.1.max(s.1);
+
+            (x0..=x1).flat_map(|x| {
+                core::iter::repeat(x).zip(y0..=y1)
+            }).all(|(x, y)| in_grid(&grid, grid_width, grid_height, (x,y)))
+        })
+        .reduce(|| ((0,0), (0,0), 0), |acc, (f, s, a)| {
+            if a > acc.2 {
+                return (f, s, a);
+            }
+
+            acc
+        });
 
-    // println!("Rectangle: {:?}", rects);
     
-    println!("Largest: {:?}", rects.last().unwrap());
+    println!("Largest: {:?}", largest);
+}
+
+fn print_grid(grid: &[Cell], width: usize, height: usize) {
+    if !PRINT {
+        return;
+    }
+
+    for y in 0..height {
+        for x in 0..width {
+            match grid[y*width+x] {
+                Cell::Empty => print!("."),
+                Cell::Red => print!("#"),
+                Cell::Green => print!("X"),
+            };
+        }
+        println!();
+    }
+}
+
+fn line_point_iter(start: (usize, usize), end: (usize, usize)) -> Box<dyn Iterator<Item = (usize, usize)>> {
+    if start.0 == end.0 {
+        let s = start.1.min(end.1);
+        let e = start.1.max(end.1);
+        Box::new(core::iter::repeat(start.0).zip(s..e).skip(1))
+    } else {
+        let s = start.0.min(end.0);
+        let e = start.0.max(end.0);
+        Box::new((s..e).zip(core::iter::repeat(start.1)).skip(1))
+    }
+}
+
+fn in_grid(grid: &[Cell], width: usize, height: usize, (x, y): (usize, usize)) -> bool {
+    if grid[y*width+x] != Cell::Empty {
+        return true;
+    }
+
+    let c = (0..x).map(|x| grid[y*width + x]).filter(|c| *c != Cell::Empty).count();
+
+    match c {
+        0 => false,
+        1 => true,
+        2 => false,
+        _ => {
+            let c = (0..y).map(|y| grid[y*width + x]).filter(|c| *c != Cell::Empty).count();
+
+            match c {
+                1 => true,
+                _ => false,
+            }
+        }
+    }
 }