diff --git a/2015/day15/main.go b/2015/day15/main.go
new file mode 100644
index 0000000..d2a4cab
--- /dev/null
+++ b/2015/day15/main.go
@@ -0,0 +1,65 @@
+package main
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/mathutil"
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func main() {
+	part1Ans, part2Ans := cookieScience(util.ReadFile("./input.txt"))
+	fmt.Printf("Part1: %d\nPart2: %d\n", part1Ans, part2Ans)
+}
+
+func cookieScience(input string) (int, int) {
+	lines := strings.Split(input, "\n")
+	cookieVals := [][]int{}
+
+	for _, line := range lines {
+		var name string
+		var cap, dur, fla, tex, cal int
+		fmt.Sscanf(line, "%s capacity %d, durability %d, flavor %d, texture %d, calories %d",
+			&name, &cap, &dur, &fla, &tex, &cal)
+
+		// trim off colons, fmt.Sscanf parses between spaces/whitespace
+		// names end up going unused...
+		name = strings.Trim(name, ":")
+
+		// cookie vals are simply all five values in order
+		cookieVals = append(cookieVals, []int{cap, dur, fla, tex, cal})
+	}
+
+	var bestScore, best500CalScore int
+	for ing1 := 0; ing1 < 100; ing1++ {
+		for ing2 := 0; ing2 < 100; ing2++ {
+			for ing3 := 0; ing3 < 100; ing3++ {
+				ing4 := 100 - ing1 - ing2 - ing3
+
+				cap := ing1*cookieVals[0][0] + ing2*cookieVals[1][0] + ing3*cookieVals[2][0] + ing4*cookieVals[3][0]
+				dur := ing1*cookieVals[0][1] + ing2*cookieVals[1][1] + ing3*cookieVals[2][1] + ing4*cookieVals[3][1]
+				fla := ing1*cookieVals[0][2] + ing2*cookieVals[1][2] + ing3*cookieVals[2][2] + ing4*cookieVals[3][2]
+				tex := ing1*cookieVals[0][3] + ing2*cookieVals[1][3] + ing3*cookieVals[2][3] + ing4*cookieVals[3][3]
+
+				cal := ing1*cookieVals[0][4] + ing2*cookieVals[1][4] + ing3*cookieVals[2][4] + ing4*cookieVals[3][4]
+
+				// make negatives zero, without this two negative scores could
+				// make a very large positive
+				cap = mathutil.MaxInt(0, cap)
+				dur = mathutil.MaxInt(0, dur)
+				fla = mathutil.MaxInt(0, fla)
+				tex = mathutil.MaxInt(0, tex)
+
+				score := cap * dur * fla * tex
+
+				if cal == 500 {
+					best500CalScore = mathutil.MaxInt(best500CalScore, score)
+				}
+				bestScore = mathutil.MaxInt(bestScore, score)
+			}
+		}
+	}
+
+	return bestScore, best500CalScore
+}
diff --git a/2015/day15/main_test.go b/2015/day15/main_test.go
new file mode 100644
index 0000000..595457f
--- /dev/null
+++ b/2015/day15/main_test.go
@@ -0,0 +1,29 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+func Test_cookieScience(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want1 int
+		want2 int
+	}{
+		{"actual both parts", util.ReadFile("input.txt"), 13882464, 11171160},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got1, got2 := cookieScience(tt.input)
+			if got1 != tt.want1 {
+				t.Errorf("cookieScience() part1 = %v, want %v", got1, tt.want1)
+			}
+			if got2 != tt.want2 {
+				t.Errorf("cookieScience() part2 = %v, want %v", got2, tt.want2)
+			}
+		})
+	}
+}