diff --git a/2025/day02/go.mod b/2025/day02/go.mod
new file mode 100644
index 0000000..379f572
--- /dev/null
+++ b/2025/day02/go.mod
@@ -0,0 +1,3 @@
+module tangled.org/seth.computer/advent-of-code/2025/day02
+
+go 1.26.2
diff --git a/2025/day02/input.txt b/2025/day02/input.txt
new file mode 100644
index 0000000..0acf68b
--- /dev/null
+++ b/2025/day02/input.txt
@@ -0,0 +1 @@
+245284-286195,797927-983972,4949410945-4949555758,115-282,8266093206-8266228431,1-21,483873-655838,419252-466133,6190-13590,3876510-4037577,9946738680-9946889090,99954692-100029290,2398820-2469257,142130432-142157371,9797879567-9798085531,209853-240025,85618-110471,35694994-35766376,4395291-4476150,33658388-33694159,680915-772910,4973452995-4973630970,52-104,984439-1009605,19489345-19604283,22-42,154149-204168,7651663-7807184,287903-402052,2244-5558,587557762-587611332,307-1038,16266-85176,422394377-422468141
diff --git a/2025/day02/main.go b/2025/day02/main.go
new file mode 100644
index 0000000..c3c2c7f
--- /dev/null
+++ b/2025/day02/main.go
@@ -0,0 +1,67 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	input, err := os.ReadFile("input.txt")
+	if err != nil {
+		log.Fatalf("failed to read file: %v", err)
+	}
+
+	invalidSum := 0
+
+	for rStr := range strings.SplitSeq(string(input), ",") {
+		r, err := parseRange(rStr)
+		if err != nil {
+			log.Fatalf("failed to parse range: %v", err)
+		}
+		for _, x := range r.findInvalid() {
+			invalidSum += x
+		}
+	}
+
+	fmt.Printf("part1: %d\n", invalidSum)
+}
+
+type idRange struct {
+	start int
+	end   int
+}
+
+func (r *idRange) findInvalid() []int {
+	var invalid []int
+	for n := r.start; n <= r.end; n++ {
+		if isRepeatedSeq(strconv.Itoa(n)) {
+			invalid = append(invalid, n)
+		}
+	}
+	return invalid
+}
+
+func isRepeatedSeq(id string) bool {
+	if len(id)%2 != 0 {
+		return false
+	}
+	half := len(id) / 2
+	fmt.Printf("%s: %s | %s\n", id, id[0:half], id[half:])
+	return id[0:half] == id[half:]
+}
+
+func parseRange(rStr string) (idRange, error) {
+	parts := strings.Split(rStr, "-")
+	start, err := strconv.Atoi(strings.TrimSpace(parts[0]))
+	if err != nil {
+		return idRange{}, fmt.Errorf("failed to parse start %q: %w", parts[0], err)
+	}
+	end, err := strconv.Atoi(strings.TrimSpace(parts[1]))
+	if err != nil {
+		return idRange{}, fmt.Errorf("failed to parse end %q: %w", parts[1], err)
+	}
+	return idRange{start: start, end: end}, nil
+}