diff --git a/year25/day10/day.go b/year25/day10/day.go
new file mode 100644
index 0000000..61c7a9d
--- /dev/null
+++ b/year25/day10/day.go
@@ -0,0 +1,269 @@
+package day10
+
+import (
+	"cmp"
+	"fmt"
+	"math"
+	"slices"
+	"strconv"
+	"strings"
+
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aoc"
+	"git.bizdoc.ro/private/devkit.git/collections/dsa"
+	"git.bizdoc.ro/private/devkit.git/gg"
+)
+
+func Part1(ctx aoc.Context) (int, error) {
+	inputLines, err := ParseInput(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("parse input: %w", err)
+	}
+	sum := 0
+	for _, line := range inputLines {
+		if line.IndicatorLight == 0 {
+			continue // zero by default
+		}
+
+		cache2 := make([]int, 1<<line.indicatorSize)
+
+		type Frame struct {
+			indicator uint64
+			step      int
+			//history   *dsa.ImmutableList[uint64]
+		}
+
+		stack := dsa.NewList[Frame]()
+		stack.Push(Frame{indicator: line.IndicatorLight, step: 0})
+
+		solution := math.MaxInt
+		for !stack.IsEmpty() {
+			item := stack.PopFront()
+			//if item.step != item.history.Len() {
+			//	panic("stack overflow")
+			//}
+			if item.indicator == 0 {
+				solution = min(solution, item.step)
+			}
+			if steps := cache2[item.indicator]; steps > 0 {
+				if steps <= item.step {
+					continue
+				}
+			}
+			cache2[item.indicator] = item.step
+			for _, button := range line.ButtonsNum {
+				if item.step <= solution {
+					stack.Push(Frame{
+						indicator: item.indicator ^ button,
+						step:      item.step + 1,
+						//history:   dsa.NewImmutableList(button, item.history),
+					})
+				}
+			}
+		}
+		sum += solution
+	}
+
+	return sum, nil
+}
+
+func compare[S ~[]E, E cmp.Ordered](s1, s2 S) (bool, bool) {
+	isSolution := true
+
+	for i := range len(s1) {
+		canContinue := s1[i] >= s2[i]
+		if !canContinue {
+			return false, false
+		}
+
+		isSolution = isSolution && (s1[i] == s2[i])
+	}
+	return true, isSolution
+}
+
+func Part2(ctx aoc.Context) (int, error) {
+	// does not work
+	inputLines, err := ParseInput(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("parse input: %w", err)
+	}
+	var sum int
+
+	for _, line := range inputLines {
+		type Frame struct {
+			state   []byte
+			step    int
+			history [][]int
+		}
+		stack := dsa.NewStack[Frame]()
+
+		startFrameJoltage := make([]byte, len(line.Joltages))
+		for i, value := range line.Joltages {
+			startFrameJoltage[i] = byte(value)
+			if value > int(startFrameJoltage[i]) {
+				panic("byte out of range")
+			}
+		}
+		stack.Push(Frame{
+			state: make([]byte, len(line.Joltages)),
+			step:  0,
+		})
+
+		solution := math.MaxInt
+		cache := make(map[string]int)
+
+		for !stack.IsEmpty() {
+			item := stack.Pop()
+			if item.step > solution {
+				continue
+			}
+
+			key := gg.UnsafeString(item.state)
+			if steps, ok := cache[key]; ok {
+				if steps < item.step {
+					continue
+				}
+			}
+			cache[key] = item.step
+
+			canContinue, isSolution := compare(startFrameJoltage, item.state)
+			if !canContinue {
+				continue
+			}
+			if isSolution {
+				//fmt.Println(item.state, item.step)
+				solution = min(solution, item.step)
+				//break
+			}
+
+			for _, button := range line.Buttons {
+				state := slices.Clone(item.state)
+				for _, val := range button {
+					state[val] += 1
+				}
+				stack.Push(Frame{
+					state: state,
+					step:  item.step + 1,
+					//history: append(slices.Clone(item.history), state),
+				})
+			}
+		}
+		ctx.Println(solution)
+		sum += solution
+	}
+
+	return sum, nil
+}
+
+func ParseInput(ctx aoc.Context) ([]InputLine, error) {
+	var inputLines []InputLine
+	scanner := ctx.Scanner()
+	for scanner.Scan() {
+		line := scanner.Text()
+		line = strings.TrimSpace(line)
+
+		input, err := ParseInputLine([]rune(line))
+		if err != nil {
+			return nil, fmt.Errorf("parse input: %w", err)
+		}
+		inputLines = append(inputLines, input)
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("scanner error: %w", err)
+	}
+	return inputLines, nil
+}
+
+type InputLine struct {
+	indicatorSize     int
+	IndicatorLight    uint64
+	IndicatorLightRaw string
+	Buttons           [][]int
+	ButtonsNum        []uint64
+	Joltages          []int
+	RawLine           string
+}
+
+func ParseInputLine(line []rune) (input InputLine, err error) {
+	// [...#.] (0,2,3,4) (2,3) (0,4) (0,1,2) (1,2,3,4) {7,5,12,7,2}
+	for i, ch := range line {
+		input.RawLine = string(line)
+		switch ch {
+		case '[': // indicator light
+			if input.IndicatorLight != 0 {
+				return input, fmt.Errorf("duplicate Indicator Light in line: %s", string(line))
+			}
+
+			size := i
+		parseIndicatorLight:
+			for i = i + 1; i < len(line); i++ {
+				switch line[i] {
+				case '#':
+					input.IndicatorLight <<= 1
+					input.IndicatorLight |= 1
+				case ']':
+					input.IndicatorLightRaw = string(line[size+1 : i])
+					size = i - size - 1
+					input.indicatorSize = size
+					break parseIndicatorLight
+				// done
+				case '.':
+					input.IndicatorLight <<= 1
+				default:
+					return input, fmt.Errorf("failed to parse Indicator Light. Unexpected character in IndicatorLight: %s", string(line))
+				}
+			}
+		case '(':
+			i += 1
+			j := strings.IndexByte(string(line[i:]), ')')
+			if j == -1 {
+				return input, fmt.Errorf("failed to parse button in line: %s", string(line))
+			}
+			button := make([]int, 0)
+			parts := strings.Split(string(line[i:i+j]), ",")
+			for _, part := range parts {
+				num, err := strconv.Atoi(part)
+				if err != nil {
+					return input, fmt.Errorf("failed to parse button in line: %s", string(line))
+				}
+				if num < 0 {
+					return input, fmt.Errorf("negative button value in line: %s", string(line))
+				}
+				if num > input.indicatorSize {
+					return input, fmt.Errorf("too many buttons in line: %s", string(line))
+				}
+				button = append(button, num)
+			}
+			input.Buttons = append(input.Buttons, button)
+			i = j
+		case '{':
+			i += 1
+			j := strings.IndexByte(string(line[i:]), '}')
+			if j == -1 {
+				return input, fmt.Errorf("failed to parse joltage in line: %s", string(line))
+			}
+			joltage := make([]int, 0)
+			parts := strings.Split(string(line[i:i+j]), ",")
+			for _, part := range parts {
+				num, err := strconv.Atoi(part)
+				if err != nil {
+					return input, fmt.Errorf("failed to parse joltage in line: %s", string(line))
+				}
+				if num < 0 {
+					return input, fmt.Errorf("negative joltage value in line: %s", string(line))
+				}
+				joltage = append(joltage, num)
+			}
+			input.Joltages = joltage
+			i = j
+		}
+	}
+
+	input.ButtonsNum = make([]uint64, len(input.Buttons))
+	for i, button := range input.Buttons {
+		for _, v := range button {
+			input.ButtonsNum[i] |= 1 << uint64(input.indicatorSize-v-1)
+		}
+	}
+	return input, nil
+}
diff --git a/year25/day10/day_test.go b/year25/day10/day_test.go
new file mode 100644
index 0000000..21bfe5d
--- /dev/null
+++ b/year25/day10/day_test.go
@@ -0,0 +1,28 @@
+package day10_test
+
+import (
+	"testing"
+
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/tests"
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/year25/day10"
+)
+
+func TestPart1Example(t *testing.T) {
+	const want = 7
+	tests.Test(t, "example.txt", tests.Handler(day10.Part1), want)
+}
+
+func TestPart1(t *testing.T) {
+	const want = 447
+	tests.Test(t, "input.txt", tests.Handler(day10.Part1), want)
+}
+
+func TestPart2Example(t *testing.T) {
+	const want = 33
+	tests.Test(t, "example.txt", tests.Handler(day10.Part2V3), want)
+}
+
+func TestPart2(t *testing.T) {
+	const want = 18960
+	tests.Test(t, "input.txt", tests.Handler(day10.Part2V3), want)
+}
diff --git a/year25/day10/v3.go b/year25/day10/v3.go
new file mode 100644
index 0000000..813bab6
--- /dev/null
+++ b/year25/day10/v3.go
@@ -0,0 +1,199 @@
+package day10
+
+import (
+	"cmp"
+	"fmt"
+	"iter"
+	"math"
+
+	"git.bizdoc.ro/gabi-public/Advent-of-Code.git/aoc"
+	"git.bizdoc.ro/private/devkit.git/collections/combinatorics/v2"
+)
+
+func Part2V3(ctx aoc.Context) (out int, err error) {
+	// https://www.reddit.com/r/adventofcode/comments/1pk87hl/2025_day_10_part_2_bifurcate_your_way_to_victory/
+
+	inputLines, err := ParseInput(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("parse input: %w", err)
+	}
+
+	for _, line := range inputLines {
+		parityMap := make(map[uint64][]ButtonSet)
+		for p := range generateButtonsCombinations(line.Buttons, len(line.Joltages)) {
+			phash := ParityHash(p.Parity)
+			parityMap[phash] = append(parityMap[phash], p)
+		}
+
+		var solve func([]int) (int, error)
+		solve = func(joltage []int) (int, error) {
+			if isFullOf(joltage, 0) {
+				return 0, nil
+			}
+
+			h := HashOfParityOf(joltage)
+			candidates, ok := parityMap[h]
+
+			if !ok {
+				return 0, fmt.Errorf("no candidates for parity")
+			}
+
+			best := math.MaxInt
+			for _, candidate := range candidates {
+				next := SubtractAndHalf(joltage, candidate.Joltages)
+
+				if !isAllGraterThan(next, 0) {
+					continue
+				}
+
+				sub, err := solve(next)
+				if err != nil {
+					continue
+				}
+
+				cost := candidate.ButtonsPresses + (2 * sub)
+				if cost < best {
+					best = cost
+				}
+			}
+
+			if best == math.MaxInt {
+				return 0, fmt.Errorf("no valid solution")
+			}
+
+			return best, nil
+		}
+
+		got, err := solve(line.Joltages)
+		if err != nil {
+			panic(err)
+		}
+		out += got
+	}
+
+	return
+}
+
+func isFullOf[T ~[]E, E comparable](s T, t E) bool {
+	for _, v := range s {
+		if v != t {
+			return false
+		}
+	}
+	return true
+}
+
+func isAllLessThan[T ~[]E, E cmp.Ordered](s T, t E) bool {
+	for _, e := range s {
+		if e >= t {
+			return false
+		}
+	}
+	return true
+}
+
+func isAllGraterThan[T ~[]E, E cmp.Ordered](s T, t E) bool {
+	for _, e := range s {
+		if e < t {
+			return false
+		}
+	}
+	return true
+}
+
+type ButtonSet struct {
+	ButtonsPresses int
+	Joltages       []int
+	Parity         []int
+}
+
+func SubtractAndHalf(j1, j2 []int) []int {
+	if len(j1) != len(j2) {
+		panic("j1 != j2")
+	}
+	j3 := make([]int, len(j1))
+	for i := range j3 {
+		j3[i] = j1[i] - j2[i]
+		if j3[i]&1 != 0 {
+			panic("j3[i] is not even")
+		}
+		j3[i] /= 2
+	}
+	return j3
+}
+
+func HashOfParityOf(jotages []int) uint64 {
+	parity := ParityOf(jotages)
+	return ParityHash(parity)
+}
+
+func ParityHash(parity []int) uint64 {
+	var k uint64
+	for i, isTrue := range parity {
+		if i > 60 {
+			panic("parity out of range")
+		}
+		mask := uint64(isTrue) << (len(parity) - i - 1)
+		k |= mask
+	}
+	return k
+}
+
+func DebugParityHashString(parity []int) string {
+	return fmt.Sprintf("%0*b", len(parity), ParityHash(parity))
+}
+
+func ParityOf(joltages []int) []int {
+	parity := make([]int, len(joltages))
+	for i := range joltages {
+		parity[i] = joltages[i] & 1
+	}
+	return parity
+}
+
+func generateButtonsCombinations(s [][]int, joltageLen int) iter.Seq[ButtonSet] {
+	buttons := make([]int, len(s))
+	for i := range buttons {
+		buttons[i] = i
+	}
+
+	return func(yield func(ButtonSet) bool) {
+		if !yield(ButtonSet{Joltages: make([]int, joltageLen), Parity: make([]int, joltageLen)}) {
+			return
+		}
+
+		joltages := make([]int, joltageLen)
+		for pattern := range generateCombinations(buttons) {
+			for i := range joltages {
+				joltages[i] = 0
+			}
+			
+			p2 := make([]int, len(pattern))
+			for i := range p2 {
+				buttonIndex := pattern[i]
+				button := s[buttonIndex]
+				for _, b := range button {
+					joltages[b] += 1
+				}
+			}
+			parity := ParityOf(joltages)
+
+			if !yield(ButtonSet{Joltages: joltages, Parity: parity, ButtonsPresses: len(pattern)}) {
+				return
+			}
+		}
+	}
+}
+
+func generateCombinations[T ~[]E, E any](arr T) iter.Seq[T] {
+	return func(yield func(T) bool) {
+		for i := range arr {
+			combs := combinatorics.NewCombinator(arr, i+1)
+			for value := range combs.Values() {
+				if !yield(value) {
+					return
+				}
+			}
+		}
+	}
+}