diff --git a/AOC.Test/Test2015.cs b/AOC.Test/Test2015.cs
index eec49db..b8b5dfe 100644
--- a/AOC.Test/Test2015.cs
+++ b/AOC.Test/Test2015.cs
@@ -20,6 +20,7 @@ public class Test2015
     [DataRow(typeof(Day12), "111754", "65402")]
     [DataRow(typeof(Day13), "733", "725")]
     [DataRow(typeof(Day14), "2655", "1059")]
+    [DataRow(typeof(Day15), "222870", "117936")]
     public void CheckAllDays(Type dayType, string part1, string part2)
     {
         Common.CheckDay(dayType, part1, part2);
@@ -37,6 +38,7 @@ public class Test2015
     [DataRow(typeof(Day09), "605", "982")]
     [DataRow(typeof(Day10), "237746", "3369156")]
     [DataRow(typeof(Day13), "330", "286")]
+    [DataRow(typeof(Day15), "62842880", "57600000")]
     public void CheckTestInputs(Type dayType, string part1, string part2)
     {
         Common.CheckDay(dayType, part1, part2, true);
diff --git a/AOC2015/Day15.cs b/AOC2015/Day15.cs
index 9137f02..0608c30 100644
--- a/AOC2015/Day15.cs
+++ b/AOC2015/Day15.cs
@@ -3,13 +3,69 @@ namespace AOC2015;
 /// <summary>
 /// Day 15: <a href="https://adventofcode.com/2015/day/15"/>
 /// </summary>
-public sealed class Day15 : Day
+public sealed partial class Day15 : Day
 {
+    [GeneratedRegex(@"-?\d+")]
+    private static partial Regex Digits();
+
+    private record Ingredient(string Name, int Capacity, int Durability, int Flavor, int Texture, int Calories);
+
+    private readonly List<Ingredient> _ingredients;
+    private readonly int _best;
+    private readonly int _best500Cals;
+
     public Day15() : base(2015, 15, "Science for Hungry People")
     {
+        _ingredients = Input.Select(ParseIngredient).ToList();
+
+        var quantities = new int[_ingredients.Count];
+        _best = 0;
+
+        while (true)
+        {
+            for (var i = 0; i < _ingredients.Count; i++)
+            {
+                quantities[i]++;
+                if (quantities[i] > 100)
+                    quantities[i] = 0;
+                else break;
+            }
+
+            var quantityApplied = quantities.Take(_ingredients.Count - 1).Sum();
+            if (quantityApplied == 0) break;
+            if (quantityApplied > 100) continue;
+
+            quantities[^1] = 100 - quantityApplied;
+
+            int cap = 0, dur = 0, fla = 0, tex = 0, cal = 0;
+            for (var j = 0; j < _ingredients.Count; j++)
+            {
+                var q = quantities[j];
+                var i = _ingredients[j];
+
+                cap += q * i.Capacity;
+                dur += q * i.Durability;
+                fla += q * i.Flavor;
+                tex += q * i.Texture;
+                cal += q * i.Calories;
+            }
+
+            var total = Math.Max(0, cap) * Math.Max(0, dur) * Math.Max(0, fla) * Math.Max(0, tex);
+
+            if (total > _best) _best = total;
+            if (total > _best500Cals && cal == 500) _best500Cals = total;
+        }
     }
 
-    public override object Part1() => "";
+    private static Ingredient ParseIngredient(string line)
+    {
+        var s = line.Split(':');
+        var nums = Digits().Matches(s[1]).Select(match => int.Parse(match.Value)).ToList();
 
-    public override object Part2() => "";
+        return new(s[0], nums[0], nums[1], nums[2], nums[3], nums[4]);
+    }
+
+    public override object Part1() => _best;
+
+    public override object Part2() => _best500Cals;
 }
diff --git a/AOC2015/input2015/test15.in b/AOC2015/input2015/test15.in
new file mode 100644
index 0000000..1a7ff25
--- /dev/null
+++ b/AOC2015/input2015/test15.in
@@ -0,0 +1,2 @@
+Butterscotch: capacity -1, durability -2, flavor 6, texture 3, calories 8
+Cinnamon: capacity 2, durability 3, flavor -2, texture -1, calories 3