diff --git a/input/day24.txt b/input/day24.txt
index e69de29..0a31990 100644
--- a/input/day24.txt
+++ b/input/day24.txt
@@ -0,0 +1,23 @@
+Immune System:
+3400 units each with 1430 hit points (immune to fire, radiation, slashing) with an attack that does 4 radiation damage at initiative 4
+138 units each with 8650 hit points (weak to bludgeoning; immune to slashing, cold, radiation) with an attack that does 576 slashing damage at initiative 16
+255 units each with 9469 hit points (weak to radiation, fire) with an attack that does 351 bludgeoning damage at initiative 8
+4145 units each with 2591 hit points (immune to cold; weak to slashing) with an attack that does 6 fire damage at initiative 12
+3605 units each with 10989 hit points with an attack that does 26 fire damage at initiative 19
+865 units each with 11201 hit points with an attack that does 102 slashing damage at initiative 10
+633 units each with 10092 hit points (weak to slashing, radiation) with an attack that does 150 slashing damage at initiative 11
+2347 units each with 3322 hit points with an attack that does 12 cold damage at initiative 2
+7045 units each with 3877 hit points (weak to radiation) with an attack that does 5 bludgeoning damage at initiative 5
+1086 units each with 8626 hit points (weak to radiation) with an attack that does 69 slashing damage at initiative 13
+
+Infection:
+2152 units each with 12657 hit points (weak to fire, cold) with an attack that does 11 fire damage at initiative 18
+40 units each with 39458 hit points (immune to radiation, fire, slashing; weak to bludgeoning) with an attack that does 1519 slashing damage at initiative 7
+59 units each with 35138 hit points (immune to radiation; weak to fire) with an attack that does 1105 fire damage at initiative 15
+1569 units each with 51364 hit points (weak to radiation) with an attack that does 55 radiation damage at initiative 17
+929 units each with 23887 hit points (weak to bludgeoning) with an attack that does 48 cold damage at initiative 14
+5264 units each with 14842 hit points (immune to cold, fire; weak to slashing, bludgeoning) with an attack that does 4 bludgeoning damage at initiative 9
+1570 units each with 30419 hit points (weak to radiation, cold; immune to fire) with an attack that does 35 slashing damage at initiative 1
+1428 units each with 21393 hit points (weak to radiation) with an attack that does 29 cold damage at initiative 6
+1014 units each with 25717 hit points (weak to fire) with an attack that does 47 fire damage at initiative 3
+7933 units each with 29900 hit points (immune to bludgeoning, radiation, slashing) with an attack that does 5 slashing damage at initiative 20
diff --git a/src/tasks/day24.rs b/src/tasks/day24.rs
index 637998d..9889b91 100644
--- a/src/tasks/day24.rs
+++ b/src/tasks/day24.rs
@@ -1,42 +1,181 @@
+use crate::utils;
+use std::cmp::Reverse;
+use std::collections::HashMap;
+
 pub fn task1() {
     let input = "Immune System:
-17 units each with 5390 hit points (weak to radiation, bludgeoning) with an attack that does 4507 fire damage at initiative 2
-989 units each with 1274 hit points (immune to fire; weak to bludgeoning, slashing) with an attack that does 25 slashing damage at initiative 3
+    17 units each with 5390 hit points (weak to radiation, bludgeoning) with an attack that does 4507 fire damage at initiative 2
+    989 units each with 1274 hit points (immune to fire; weak to bludgeoning, slashing) with an attack that does 25 slashing damage at initiative 3
 
 Infection:
-801 units each with 4706 hit points (weak to radiation) with an attack that does 116 bludgeoning damage at initiative 1
-4485 units each with 2961 hit points (immune to radiation; weak to fire, cold) with an attack that does 12 slashing damage at initiative 4";
-    let mut groups_immune: Vec<Group> = Vec::new();
-    let mut groups_infection: Vec<Group> = Vec::new();
+    801 units each with 4706 hit points (weak to radiation) with an attack that does 116 bludgeoning damage at initiative 1
+    4485 units each with 2961 hit points (immune to radiation; weak to fire, cold) with an attack that does 12 slashing damage at initiative 4";
+    let input = utils::read_file("input/day24.txt");
+    let mut game = Game::create(&input);
 
-    let mut to_immune = false;
-    for line in input.lines() {
-        match line {
-            "Immune System:" => {
-                to_immune = true;
-            }
-            "Infection:" => {
-                to_immune = false;
-            }
-            "" => (),
-            group => {
-                if let Some(group) = Group::from_str(group) {
-                    if to_immune {
-                        groups_immune.push(group);
-                    } else {
-                        groups_infection.push(group);
+    println!(
+        "Immune start units: {}",
+        game.groups
+            .iter()
+            .filter(|(_, it)| it.team == Team::ImmuneSystem)
+            .map(|(_, it)| it.units)
+            .sum::<i64>()
+    );
+    println!(
+        "Infection start units: {}",
+        game.groups
+            .iter()
+            .filter(|(_, it)| it.team == Team::Infection)
+            .map(|(_, it)| it.units)
+            .sum::<i64>()
+    );
+
+    let mut rounds_played = 0;
+    while !game.is_over() {
+        game.round();
+        rounds_played += 1;
+    }
+
+    println!("{:#?}", game);
+    println!("Played {} rounds", rounds_played);
+
+    println!(
+        "Standing units after the game: {}",
+        game.groups.iter().map(|(_, it)| it.units).sum::<i64>()
+    );
+
+    // 21107 too high
+    // 21004 too high
+}
+
+#[derive(Debug)]
+struct Game {
+    groups: HashMap<usize, Group>,
+}
+
+impl Game {
+    fn create(input: &str) -> Self {
+        let mut groups = HashMap::new();
+        let mut team = Team::ImmuneSystem;
+        for (id, line) in input.lines().enumerate() {
+            match line {
+                "Immune System:" => {
+                    team = Team::ImmuneSystem;
+                }
+                "Infection:" => {
+                    team = Team::Infection;
+                }
+                "" => (),
+                group => {
+                    if let Some(group) = Group::from_str(group, team, id) {
+                        groups.insert(id, group);
                     }
                 }
             }
         }
+        Game { groups }
     }
 
-    println!("Immune System:\n{:?}", groups_immune);
-    println!("Infection:\n{:?}", groups_infection);
+    fn round(&mut self) {
+        let mut target: HashMap<usize, usize> = HashMap::new();
+        // lock targets ordered by effective power
+        let mut all_by_power: Vec<&Group> = self.groups.iter().map(|(_, it)| it).collect();
+        all_by_power.sort_unstable_by_key(|a| Reverse((a.effective_power(), a.initiative)));
+        // for group in all_by_power.iter() {
+        //     println!(
+        //         "{}: {} ({})",
+        //         group.id,
+        //         group.effective_power(),
+        //         group.initiative
+        //     );
+        // }
+        // println!("{:?}", all_by_power);
+        for group in all_by_power.iter() {
+            if let Some(t) = self
+                .groups
+                .iter()
+                .map(|(_, it)| it)
+                .filter(|it| it.team != group.team)
+                .filter(|it| !target.values().any(|t| *t == it.id))
+                // .filter(|it| group.compute_attack_damage_to(&it) >= it.hp_each)
+                // .inspect(|it| {
+                //     println!(
+                //         "{} would deal {} damage to {}",
+                //         group.id,
+                //         group.compute_attack_damage_to(it),
+                //         it.id
+                //     )
+                // })
+                .max_by_key(|it| {
+                    (
+                        group.compute_attack_damage_to(&it),
+                        it.effective_power(),
+                        it.initiative,
+                    )
+                })
+            {
+                if group.compute_attack_damage_to(&t) <= 0 {
+                    println!(
+                        "Didn't find a target where {:?} can deal positive damage.",
+                        group
+                    );
+                    continue;
+                } else {
+                    target.insert(group.id, t.id);
+                }
+            }
+        }
+
+        // attack ordered by initiative
+        let mut all_ids_by_initiative: Vec<usize> =
+            self.groups.iter().map(|(_, it)| it.id).collect();
+        all_ids_by_initiative.sort_unstable_by_key(|id| Reverse(self.groups[id].initiative));
+
+        for active_id in all_ids_by_initiative {
+            if !self.groups[&active_id].alive() {
+                // was killed in this round
+                println!("Group {} already dead", active_id);
+                continue;
+            }
+            if let Some(enemy_id) = target.get(&active_id) {
+                let enemy = &self.groups[enemy_id];
+                let damage: i64 = self.groups[&active_id].compute_attack_damage_to(&enemy);
+                let dying_units = damage / enemy.hp_each;
+                if let Some(enemy) = self.groups.get_mut(enemy_id) {
+                    enemy.units -= dying_units;
+                }
+                // println!(
+                //     "{} dealt {} ({} units) damage to {}",
+                //     active_id, damage, dying_units, enemy_id
+                // );
+            }
+        }
+
+        // clean up dead groups
+        self.groups.retain(|_, it| it.alive());
+        // println!("{:?}", self.groups);
+    }
+
+    fn is_over(&self) -> bool {
+        self.groups.len() == 0
+            || self.groups.iter().all(|(_, it)| it.team == Team::Infection)
+            || self
+                .groups
+                .iter()
+                .all(|(_, it)| it.team == Team::ImmuneSystem)
+    }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Copy, Clone, PartialEq)]
+enum Team {
+    Infection,
+    ImmuneSystem,
+}
+
+#[derive(Debug, Clone)]
 struct Group {
+    id: usize,
+    team: Team,
     units: i64,
     hp_each: i64,
     weaknesses: Vec<String>,
@@ -47,7 +186,7 @@ struct Group {
 }
 
 impl Group {
-    fn from_str(input: &str) -> Option<Self> {
+    fn from_str(input: &str, team: Team, id: usize) -> Option<Self> {
         // 801 units each with 4706 hit points (weak to radiation) with an attack that does 116 bludgeoning damage at initiative 1
         use regex::Regex;
         let regex = Regex::new(r"(\d+) units each with (\d+) hit points \((.+)\) with an attack that does (\d+) (\w+) damage at initiative (\d+)").unwrap();
@@ -68,6 +207,8 @@ impl Group {
             }
 
             let group = Group {
+                id,
+                team,
                 units,
                 hp_each,
                 weaknesses,
@@ -81,4 +222,29 @@ impl Group {
             None
         }
     }
+
+    fn alive(&self) -> bool {
+        self.units > 0
+    }
+
+    fn effective_power(&self) -> i64 {
+        if !self.alive() {
+            panic!("I have no power, im dead!")
+        }
+        self.units * self.attack_damage
+    }
+
+    fn compute_attack_damage_to(&self, other: &Self) -> i64 {
+        if self.alive() {
+            if other.weaknesses.contains(&self.attack_type) {
+                self.effective_power() * 2
+            } else if other.immunities.contains(&self.attack_type) {
+                0
+            } else {
+                self.effective_power()
+            }
+        } else {
+            panic!("I'm not alive, I cannot attack anyone")
+        }
+    }
 }