diff --git a/src/bin/day12.rs b/src/bin/day12.rs
new file mode 100644
index 0000000..2cc838c
--- /dev/null
+++ b/src/bin/day12.rs
@@ -0,0 +1,160 @@
+use std::time::Instant;
+
+use aoc_2025::{Grid, load, print_res};
+use bstr::{BString, ByteSlice};
+use color_eyre::eyre::Context;
+
+#[derive(PartialEq, Eq)]
+enum ShapeSlot {
+    Full,
+    Empty,
+}
+
+pub struct Shape(Grid<ShapeSlot>);
+
+impl std::fmt::Display for ShapeSlot {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ShapeSlot::Full => write!(f, "#"),
+            ShapeSlot::Empty => write!(f, "."),
+        }
+    }
+}
+
+impl std::fmt::Debug for Shape {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.0)
+    }
+}
+
+#[derive(Debug)]
+pub struct Region {
+    lines: usize,
+    cols: usize,
+    shapes: Vec<u8>,
+}
+
+type Parsed = (Vec<Shape>, Vec<Region>);
+
+#[inline(never)]
+pub fn parsing(input: &BString) -> color_eyre::Result<Parsed> {
+    let mut parts = input.split_str("\n\n").peekable();
+    let mut shapes = Vec::new();
+
+    for i in 0.. {
+        let Some(&part) = parts.peek() else {
+            color_eyre::eyre::bail!("Unexpected end of input\n");
+        };
+        let expect = format!("{i}:\n");
+
+        if !part.starts_with_str(&expect) {
+            break;
+        }
+
+        let part = parts.next().unwrap();
+
+        let line_len = part.lines().nth(1).unwrap().len();
+        let values = part
+            .lines()
+            .skip(1)
+            .flat_map(|l| {
+                l.iter().map(|&b| match b {
+                    b'.' => Ok(ShapeSlot::Empty),
+                    b'#' => Ok(ShapeSlot::Full),
+                    _ => Err(color_eyre::eyre::eyre!("Invalid grid point: {}", b as char)),
+                })
+            })
+            .collect::<Result<_, _>>()?;
+
+        shapes.push(Shape(Grid::new(values, line_len)));
+    }
+
+    let Some(regions) = parts.next() else {
+        color_eyre::eyre::bail!("Unexpected end on input\n")
+    };
+
+    color_eyre::eyre::ensure!(parts.count() == 0, "Too many parts of the input");
+
+    Ok((
+        shapes,
+        str::from_utf8(regions)?
+            .lines()
+            .map(|line| {
+                let Some((size, shapes)) = line.split_once(": ") else {
+                    color_eyre::eyre::bail!("Malformed region: {line}");
+                };
+
+                let Some((lines, cols)) = size.split_once('x') else {
+                    color_eyre::eyre::bail!("Malformed region size: {size}");
+                };
+
+                Ok(Region {
+                    lines: lines
+                        .parse()
+                        .wrap_err_with(|| format!("While parsing lines: {lines}"))?,
+                    cols: cols
+                        .parse()
+                        .wrap_err_with(|| format!("While parsing cols: {cols}"))?,
+                    shapes: shapes
+                        .split_whitespace()
+                        .map(|n| {
+                            n.parse()
+                                .wrap_err_with(|| format!("While parsing shape: {n}"))
+                        })
+                        .collect::<Result<_, _>>()?,
+                })
+            })
+            .collect::<Result<_, _>>()?,
+    ))
+}
+
+#[inline(never)]
+pub fn part1((shapes, regions): Parsed) {
+    let shape_areas: Vec<_> = shapes.iter().map(|s| s.0.count(&ShapeSlot::Full)).collect();
+    let mut remain = 0;
+
+    for region in regions {
+        let area = region.lines * region.cols;
+        let min_area: usize = region
+            .shapes
+            .iter()
+            .zip(&shape_areas)
+            .map(|(&n, &a)| n as usize * a)
+            .sum();
+
+        // Not enough area to even attempt
+        if min_area > area {
+            continue
+        }
+
+        remain += 1;
+    }
+
+    print_res!("Possible solvable: {remain}");
+}
+
+#[inline(never)]
+pub fn part2(input: Parsed) {
+    todo!("todo part2")
+}
+
+pub fn main() -> color_eyre::Result<()> {
+    let context = load()?;
+
+    let start = Instant::now();
+    let parsed = parsing(&context.input)?;
+    let elapsed = humantime::format_duration(start.elapsed());
+
+    let start = Instant::now();
+    if context.part == 1 {
+        part1(parsed);
+    } else {
+        part2(parsed);
+    }
+    let elapsed_part = humantime::format_duration(start.elapsed());
+
+    println!("  Parsing: {elapsed}");
+    println!("  Solving: {elapsed_part}");
+
+    Ok(())
+}
diff --git a/src/lib.rs b/src/lib.rs
index 264dc84..1c75b3a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -69,6 +69,10 @@ impl<T: PartialEq + Eq> Grid<T> {
         }
         sum
     }
+
+    pub fn count(&self, like: &T) -> usize {
+        self.values.iter().filter(|&v| v == like).count()
+    }
 }
 
 impl<T> std::ops::Index<(usize, usize)> for Grid<T> {