diff --git a/input/day10.txt b/input/day10.txt
new file mode 100644
index 0000000..6a9f2d1
--- /dev/null
+++ b/input/day10.txt
@@ -0,0 +1,5 @@
+.#..#
+.....
+#####
+....#
+...##
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 33ea898..eb31e43 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,5 @@
 mod tasks;
 
 fn main() {
-    tasks::day09::run();
+    tasks::day10::run();
 }
diff --git a/src/tasks/day09.rs b/src/tasks/day09.rs
index 269703c..eddc162 100644
--- a/src/tasks/day09.rs
+++ b/src/tasks/day09.rs
@@ -1,5 +1,6 @@
 use super::day05::{IntCodeComputer, RAM};
 
+#[allow(dead_code)]
 pub fn run() {
     let input = std::fs::read_to_string("input/day09.txt").unwrap();
     let ram: RAM = input
diff --git a/src/tasks/day10.rs b/src/tasks/day10.rs
new file mode 100644
index 0000000..dec8ed3
--- /dev/null
+++ b/src/tasks/day10.rs
@@ -0,0 +1,71 @@
+use std::collections::HashSet;
+
+#[allow(dead_code)]
+pub fn run() {
+    let asteroids: HashSet<(i32, i32)> = std::fs::read_to_string("input/day10.txt")
+        .unwrap()
+        .lines()
+        .enumerate()
+        .map(|(y, line)| {
+            line.chars()
+                .enumerate()
+                .filter(|(_, it)| *it == '#')
+                .map(move |(x, _)| (x as i32, y as i32))
+        })
+        .flatten()
+        .collect();
+    task1(&asteroids);
+}
+
+fn task1(asteroids: &HashSet<(i32, i32)>) {
+    let max = asteroids
+        .iter()
+        .map(|asteroid| {
+            //println!("inspecting {:?}", asteroid);
+            // map to number of other asteroids it sees
+            let mut others = asteroids.clone();
+            others.remove(&asteroid);
+            // count those asteroids that are not blocked by another
+            let count = others
+                .iter()
+                .filter(|target| {
+                    !others
+                        .iter()
+                        .any(|occluder| blocks_view(*asteroid, **target, *occluder))
+                })
+                //.inspect(|target| println!("sees {:?}", target))
+                .count();
+            println!("{:?}: {}", asteroid, count);
+            count
+        })
+        .max()
+        .unwrap();
+    println!(
+        "Task 1: maximum visible asteroids from another asteroid are {}",
+        max
+    ); //283 too high, 257 too low
+}
+
+fn blocks_view(pov: (i32, i32), target: (i32, i32), occluder: (i32, i32)) -> bool {
+    let ux = occluder.0 - pov.0;
+    let uy = occluder.1 - pov.1;
+
+    let sx = (target.0 - pov.0) as f32 / ux as f32;
+    let sy = (target.1 - pov.1) as f32 / uy as f32;
+    //dbg!((ux, uy, sx, sy));
+    match (ux, uy) {
+        (0, _) => sy.abs() > 1.0 && target.0 == pov.0,
+        (_, 0) => sx.abs() > 1.0 && target.1 == pov.1,
+        (_, _) => sx.abs() > 1.0 && sx == sy,
+    }
+}
+
+mod test {
+    #[test]
+    fn block_test() {
+        assert_eq!(true, super::blocks_view((3, 4), (1, 0), (2, 2)));
+        assert_ne!(true, super::blocks_view((3, 4), (2, 2), (1, 0)));
+        assert_ne!(true, super::blocks_view((3, 4), (1, 0), (1, 2)));
+        assert_eq!(true, super::blocks_view((4, 4), (4, 0), (4, 3)));
+    }
+}
diff --git a/src/tasks/mod.rs b/src/tasks/mod.rs
index 30a8d06..5c5d3bb 100644
--- a/src/tasks/mod.rs
+++ b/src/tasks/mod.rs
@@ -6,3 +6,4 @@ pub mod day06;
 pub mod day07;
 pub mod day08;
 pub mod day09;
+pub mod day10;