diff --git a/Cargo.lock b/Cargo.lock
index a5ddce5..08638a6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -34,6 +34,20 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "day1"
 version = "0.1.0"
 
+[[package]]
+name = "day10"
+version = "0.1.0"
+dependencies = [
+ "itertools 0.8.2 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "day11"
+version = "0.1.0"
+dependencies = [
+ "shared 0.1.0",
+]
+
 [[package]]
 name = "day2"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 22d3d1f..81ada48 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -9,5 +9,7 @@ members = [
 	"day7",
 	"day8",
 	"day9",
+	"day10",
+	"day11",
 	"shared",
 ]
diff --git a/day10/Cargo.toml b/day10/Cargo.toml
new file mode 100644
index 0000000..f25f0cf
--- /dev/null
+++ b/day10/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "day10"
+version = "0.1.0"
+authors = ["Stefan Bühler <stbuehler@web.de>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+itertools = "0.8.2"
diff --git a/day10/src/input.txt b/day10/src/input.txt
new file mode 100644
index 0000000..defc148
--- /dev/null
+++ b/day10/src/input.txt
@@ -0,0 +1,26 @@
+#.#.###.#.#....#..##.#....
+.....#..#..#..#.#..#.....#
+.##.##.##.##.##..#...#...#
+#.#...#.#####...###.#.#.#.
+.#####.###.#.#.####.#####.
+#.#.#.##.#.##...####.#.##.
+##....###..#.#..#..#..###.
+..##....#.#...##.#.#...###
+#.....#.#######..##.##.#..
+#.###.#..###.#.#..##.....#
+##.#.#.##.#......#####..##
+#..##.#.##..###.##.###..##
+#..#.###...#.#...#..#.##.#
+.#..#.#....###.#.#..##.#.#
+#.##.#####..###...#.###.##
+#...##..#..##.##.#.##..###
+#.#.###.###.....####.##..#
+######....#.##....###.#..#
+..##.#.####.....###..##.#.
+#..#..#...#.####..######..
+#####.##...#.#....#....#.#
+.#####.##.#.#####..##.#...
+#..##..##.#.##.##.####..##
+.##..####..#..####.#######
+#.#..#.##.#.######....##..
+.#.##.##.####......#.##.##
diff --git a/day10/src/main.rs b/day10/src/main.rs
new file mode 100644
index 0000000..1847618
--- /dev/null
+++ b/day10/src/main.rs
@@ -0,0 +1,107 @@
+use itertools::Itertools;
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct Position {
+	pub x: usize,
+	pub y: usize,
+}
+
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct Field {
+	rows: usize,
+	columns: usize,
+	astroids: Vec<bool>,
+}
+
+fn gcd(mut x: isize, mut y: isize) -> isize {
+	loop {
+		if y == 0 { return x; }
+		x = x % y;
+		if x == 0 { return y; }
+		y = y % x;
+	}
+}
+
+impl Field {
+	pub fn parse(input: &str) -> Self {
+		let lines = input.lines().collect::<Vec<_>>();
+		let rows = lines.len();
+		let columns = lines[0].len();
+		let mut astroids = Vec::new();
+		for line in lines {
+			assert_eq!(columns, line.len());
+			for cell in line.chars() {
+				astroids.push(match cell {
+					'#' => true,
+					'.' => false,
+					_ => panic!("Unexpected cell: {:?}", cell),
+				})
+			}
+		}
+
+		Self {
+			rows,
+			columns,
+			astroids,
+		}
+	}
+
+	pub fn sees(&self, a: Position, b: Position) -> bool {
+		if a == b { return true; }
+		let diff_x = b.x as isize - a.x as isize;
+		let diff_y = b.y as isize - a.y as isize;
+		let d = gcd(diff_x, diff_y).abs();
+		let diff_x = diff_x / d;
+		let diff_y = diff_y / d;
+		let mut pos = a;
+		loop {
+			pos.x = (pos.x as isize + diff_x) as usize;
+			pos.y = (pos.y as isize + diff_y) as usize;
+			if pos == b { return true; }
+			if self[pos] { return false; }
+		}
+	}
+
+	pub fn all_astroids(&self) -> impl Iterator<Item = Position> + '_ {
+		(0..self.columns).cartesian_product(0..self.rows).map(|(x, y)| Position { x, y }).filter(move |pos| self[*pos])
+	}
+
+	pub fn best_monitoring_station(&self) -> (Position, usize) {
+		self.all_astroids().map(|monitor| {
+			// can see itself, but only count "others"
+			(monitor, self.all_astroids().filter(|astroid| self.sees(monitor, *astroid)).count() - 1)
+		}).max_by_key(|(_, n)| *n).unwrap()
+	}
+}
+
+impl std::ops::Index<Position> for Field {
+	type Output = bool;
+
+	fn index(&self, index: Position) -> &Self::Output {
+		assert!(index.x < self.columns);
+		assert!(index.y < self.rows);
+		&self.astroids[index.y * self.columns + index.x]
+	}
+}
+
+fn main() {
+	let input = include_str!("input.txt");
+	println!("Best monitoring station sees astroids: {}", Field::parse(input).best_monitoring_station().1);
+}
+
+#[cfg(test)]
+mod day10test {
+	use super::*;
+
+	#[test]
+	fn examples1() {
+		assert_eq!(
+			Field::parse(".#..#
+.....
+#####
+....#
+...##").best_monitoring_station(),
+			(Position { x: 3, y: 4 }, 8),
+		);
+	}
+}
\ No newline at end of file
diff --git a/day11/Cargo.toml b/day11/Cargo.toml
new file mode 100644
index 0000000..f50d1ba
--- /dev/null
+++ b/day11/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "day11"
+version = "0.1.0"
+authors = ["Stefan Bühler <stbuehler@web.de>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+shared = { path = "../shared" }
diff --git a/day11/src/input.txt b/day11/src/input.txt
new file mode 100644
index 0000000..864e55e
--- /dev/null
+++ b/day11/src/input.txt
@@ -0,0 +1 @@
+3,8,1005,8,309,1106,0,11,0,0,0,104,1,104,0,3,8,102,-1,8,10,101,1,10,10,4,10,1008,8,1,10,4,10,1001,8,0,29,3,8,102,-1,8,10,101,1,10,10,4,10,1008,8,0,10,4,10,102,1,8,51,3,8,102,-1,8,10,1001,10,1,10,4,10,108,0,8,10,4,10,1002,8,1,72,1,1104,8,10,2,1105,15,10,2,1106,0,10,3,8,1002,8,-1,10,1001,10,1,10,4,10,1008,8,1,10,4,10,101,0,8,107,3,8,102,-1,8,10,1001,10,1,10,4,10,108,1,8,10,4,10,101,0,8,128,2,6,8,10,3,8,102,-1,8,10,101,1,10,10,4,10,1008,8,0,10,4,10,102,1,8,155,1006,0,96,2,108,10,10,1,101,4,10,3,8,1002,8,-1,10,101,1,10,10,4,10,1008,8,0,10,4,10,1002,8,1,188,2,1,5,10,3,8,102,-1,8,10,101,1,10,10,4,10,1008,8,0,10,4,10,102,1,8,214,2,6,18,10,1006,0,78,1,105,1,10,3,8,1002,8,-1,10,1001,10,1,10,4,10,1008,8,1,10,4,10,102,1,8,247,2,103,8,10,2,1002,10,10,2,106,17,10,1,1006,15,10,3,8,102,-1,8,10,101,1,10,10,4,10,1008,8,1,10,4,10,101,0,8,285,1,1101,18,10,101,1,9,9,1007,9,992,10,1005,10,15,99,109,631,104,0,104,1,21102,387507921664,1,1,21102,1,326,0,1106,0,430,21102,932826591260,1,1,21102,337,1,0,1106,0,430,3,10,104,0,104,1,3,10,104,0,104,0,3,10,104,0,104,1,3,10,104,0,104,1,3,10,104,0,104,0,3,10,104,0,104,1,21101,206400850983,0,1,21101,0,384,0,1105,1,430,21102,3224464603,1,1,21102,395,1,0,1106,0,430,3,10,104,0,104,0,3,10,104,0,104,0,21102,838433657700,1,1,21102,418,1,0,1106,0,430,21101,825012007272,0,1,21101,429,0,0,1106,0,430,99,109,2,21202,-1,1,1,21101,40,0,2,21101,461,0,3,21102,1,451,0,1105,1,494,109,-2,2105,1,0,0,1,0,0,1,109,2,3,10,204,-1,1001,456,457,472,4,0,1001,456,1,456,108,4,456,10,1006,10,488,1102,1,0,456,109,-2,2106,0,0,0,109,4,1202,-1,1,493,1207,-3,0,10,1006,10,511,21101,0,0,-3,21202,-3,1,1,21201,-2,0,2,21102,1,1,3,21102,1,530,0,1106,0,535,109,-4,2106,0,0,109,5,1207,-3,1,10,1006,10,558,2207,-4,-2,10,1006,10,558,22101,0,-4,-4,1106,0,626,22102,1,-4,1,21201,-3,-1,2,21202,-2,2,3,21101,0,577,0,1106,0,535,22102,1,1,-4,21101,1,0,-1,2207,-4,-2,10,1006,10,596,21102,0,1,-1,22202,-2,-1,-2,2107,0,-3,10,1006,10,618,21201,-1,0,1,21102,618,1,0,105,1,493,21202,-2,-1,-2,22201,-4,-2,-4,109,-5,2105,1,0
diff --git a/day11/src/main.rs b/day11/src/main.rs
new file mode 100644
index 0000000..52f273b
--- /dev/null
+++ b/day11/src/main.rs
@@ -0,0 +1,107 @@
+use shared::intcode::{IntCode, SimulateStep};
+use std::collections::{HashMap, HashSet};
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub enum Direction {
+	Up,
+	Right,
+	Down,
+	Left,
+}
+
+impl Direction {
+	pub fn turn_right(self) -> Self {
+		match self {
+			Self::Up => Self::Right,
+			Self::Right => Self::Down,
+			Self::Down => Self::Left,
+			Self::Left => Self::Up,
+		}
+	}
+
+	pub fn turn_left(self) -> Self {
+		match self {
+			Self::Up => Self::Left,
+			Self::Right => Self::Up,
+			Self::Down => Self::Right,
+			Self::Left => Self::Down,
+		}
+	}
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
+pub struct Position {
+	pub x: isize,
+	pub y: isize,
+}
+
+impl std::ops::Add<Direction> for Position {
+	type Output = Position;
+
+	fn add(mut self, rhs: Direction) -> Self::Output {
+		match rhs {
+			Direction::Up => self.y -= 1,
+			Direction::Right => self.x += 1,
+			Direction::Down => self.y += 1,
+			Direction::Left => self.x -= 1,
+		}
+		self
+	}
+}
+
+fn paint(mut ic: IntCode, start_white: bool) -> HashMap<Position, bool> {
+	let mut painted = HashMap::new();
+	let mut pos = Position { x: 0, y: 0 };
+	let mut direction = Direction::Up;
+	if start_white {
+		painted.insert(pos, true);
+	}
+	loop {
+		let is_white = painted.get(&pos).cloned().unwrap_or(false);
+		ic.next_input = Some(if is_white { 1 } else { 0 });
+		match ic.simulate_step() {
+			SimulateStep::WaitForInput => panic!("no further input until paint and movement done"),
+			SimulateStep::Finished => break,
+			SimulateStep::Output(n) => {
+				match n {
+					0 => { painted.insert(pos, false); },
+					1 => { painted.insert(pos, true); },
+					_ => panic!("invalid paint: {}", n),
+				}
+			}
+		}
+		match ic.simulate_step().expect_output() {
+			0 => direction = direction.turn_left(),
+			1 => direction = direction.turn_right(),
+			n => panic!("invalid rotation: {}", n),
+		}
+		pos = pos + direction;
+	}
+	painted
+}
+
+fn visualize(painted: HashMap<Position, bool>) {
+	let painted_white: HashSet<Position> = painted.into_iter().filter_map(|(k, v)| if v { Some(k) } else { None }).collect();
+	let left = painted_white.iter().map(|p| p.x).min().unwrap();
+	let right = painted_white.iter().map(|p| p.x).max().unwrap();
+	let top = painted_white.iter().map(|p| p.y).min().unwrap();
+	let bottom = painted_white.iter().map(|p| p.y).max().unwrap();
+	for y in top..=bottom {
+		for x in left..=right {
+			if painted_white.contains(&Position { x, y }) {
+				print!("#");
+			} else {
+				print!(" ");
+			}
+		}
+		println!("");
+	}
+}
+
+fn main() {
+	let ic = include_str!("input.txt").parse::<IntCode>().unwrap();
+	let painted = paint(ic.clone(), false);
+	println!("First try: Painted {} tiles.", painted.len());
+	let painted = paint(ic, true);
+	visualize(painted);
+}