diff --git a/day20/example.txt b/day20/example.txt
deleted file mode 100644
index e69de29..0000000
diff --git a/day20/input.txt b/day20/input.txt
index e69de29..c2efe97 100644
--- a/day20/input.txt
+++ b/day20/input.txt
@@ -0,0 +1,58 @@
+%vg -> lf, vd
+%dr -> kg
+%cn -> mv, pt
+%rq -> bk, gr
+%vp -> lp, bk
+%kg -> lv
+%lv -> jc, tp
+%sj -> rm, vd
+%jc -> tp, qr
+%km -> tp, dr
+%jx -> cn
+&vd -> tf, lf, nb, cx, hx, lr
+%lp -> jt, bk
+%vj -> ps
+broadcaster -> km, lr, xh, rf
+%dj -> pt, gc
+%cg -> vd, hx
+&ln -> tg
+%fl -> pt, sk
+%lm -> tr, bk
+%lr -> vd, vg
+&pt -> vq, rf, cm, jx, rg
+%cx -> gp
+%gp -> vd, sj
+&db -> tg
+%st -> vd
+%jt -> bk
+%jh -> lm, bk
+%xf -> bd, tp
+%gc -> cm, pt
+&tp -> dr, km, kg, db, vj, qr
+%ps -> xf, tp
+%rf -> pt, dj
+%lf -> nb
+%bd -> tp, gg
+%dk -> tp, vj
+%mn -> jh, bk
+&tg -> rx
+%ql -> bk, zx
+%tr -> bk, vp
+%sk -> pt
+%nb -> cg
+%sb -> vd, cx
+%qr -> dk
+%xh -> bk, ql
+%rg -> sd
+%hx -> sb
+%sd -> pt, jx
+%gr -> bk, mn
+%gg -> tp
+%zx -> rq
+&bk -> xh, ln, zx
+%rm -> st, vd
+%hq -> fl, pt
+&vq -> tg
+%cm -> rg
+&tf -> tg
+%mv -> pt, hq
diff --git a/day20/main.go b/day20/main.go
index c0596d8..6b8b413 100644
--- a/day20/main.go
+++ b/day20/main.go
@@ -4,8 +4,11 @@ import (
 	"bufio"
 	_ "embed"
 	"fmt"
+	"os"
+	"strings"
 
 	aoc "go.sour.is/advent-of-code"
+	"golang.org/x/exp/maps"
 )
 
 // var log = aoc.Log
@@ -20,11 +23,357 @@ type result struct {
 func (r result) String() string { return fmt.Sprintf("%#v", r) }
 
 func run(scan *bufio.Scanner) (*result, error) {
-
-	for scan.Scan() {
-		_ = scan.Text()
-
+	var forever bool
+	if os.Getenv("AOC_FOREVER") == "1" {
+		forever = true
 	}
 
-	return &result{}, nil
+	m := &machine{}
+	receivers := make(map[string][]string)
+
+	m.Add("rx", &rx{})
+
+	for scan.Scan() {
+		text := scan.Text()
+
+		name, text, _ := strings.Cut(text, " -> ")
+		dest := strings.Split(text, ", ")
+
+		switch {
+		case name == "broadcaster":
+			m.Add(name, &broadcaster{dest: dest})
+		case strings.HasPrefix(name, "%"):
+			name = strings.TrimPrefix(name, "%")
+			m.Add(name, &flipflop{name: name, dest: dest})
+
+		case strings.HasPrefix(name, "&"):
+			name = strings.TrimPrefix(name, "&")
+			m.Add(name, &conjuction{name: name, dest: dest})
+		}
+
+		for _, d := range dest {
+			receivers[d] = append(receivers[d], name)
+		}
+	}
+
+	m.Setup(receivers)
+
+	result := &result{}
+
+	if forever {
+		i := 0
+
+		defer func() {
+			if p := recover(); p != nil {
+				fmt.Printf("## Press %d FINISH %v ##", i, p)
+				os.Exit(1)
+			}
+		}()
+
+		for {
+			if i%12345 == 0 {
+				fmt.Printf("## Press %d ##\r", i)
+			}
+			m.Push(i)
+			i++
+		}
+	}
+
+	for i := 0; i < 4_0000; i++ {
+		// fmt.Printf("\n## Press %d ##\n\n", i)
+		if i == 1000 {
+			result.valuePT1 = m.highPulses * m.lowPulses
+		}
+		m.Push(i)
+		
+	}
+
+	// fmt.Println("\n## SUMMARY ##")
+	// fmt.Println("Sent", LOW, m.lowPulses)
+	// fmt.Println("Sent", HIGH, m.highPulses)
+	var lvalues []int
+
+	for _, p := range m.m {
+		if p, ok := p.(*conjuction); ok && in(p.name, []string{"bk","tp","pt","vd"}) {
+			var values []int
+			for k, v := range p.pushes {
+				for i, h := range makeHistory(v) {
+					if i == 1 && len(h) > 3 && h[0] > 0 { //&& all(h[0], h[1:]...) {
+						fmt.Println(p.name, k, i, h[0])
+						values = append(values, h[0])
+					}
+				}
+			}
+			max := aoc.Max(values[0], values...)
+			fmt.Println(p.name, "MAX", max, values)
+			lvalues = append(lvalues, max)
+		}
+	}
+	result.valuePT2 = aoc.LCM(lvalues...)
+	fmt.Println("tg", "LCM", result.valuePT2, lvalues)
+
+	// trace("rx", receivers)
+
+	return result, nil
+}
+
+type signal bool
+
+const (
+	LOW  signal = false
+	HIGH signal = true
+)
+
+func (m signal) String() string {
+	if m {
+		return " >>-HIGH-> "
+	}
+	return " >>-LOW-> "
+}
+
+type message struct {
+	signal
+	from, to string
+}
+
+func (m message) String() string {
+	return fmt.Sprint(m.from, m.signal, m.to)
+}
+
+type pulser interface {
+	Pulse(message)
+	SetMachine(*machine)
+}
+
+type machine struct {
+	m map[string]pulser
+	press int
+
+	queue []message
+	hwm   int
+
+	stop bool
+
+	highPulses int
+	lowPulses  int
+}
+
+func (m *machine) Add(name string, p pulser) {
+	if m.m == nil {
+		m.m = make(map[string]pulser)
+	}
+	p.SetMachine(m)
+	m.m[name] = p
+}
+func (m *machine) Send(msgs ...message) {
+	m.queue = append(m.queue, msgs...)
+	for _, msg := range msgs {
+		// fmt.Println(msg)
+		if msg.signal {
+			m.highPulses++
+		} else {
+			m.lowPulses++
+		}
+	}
+}
+
+func (m *machine) Push(i int) {
+	m.press = i
+	m.Send(generate(LOW, "button", "broadcaster")...)
+	m.processQueue(i)
+}
+
+func (m *machine) processQueue(i int) {
+	// look for work and process up to the queue length. repeat.
+	hwm := 0
+	for hwm < len(m.queue) {
+		end := len(m.queue)
+
+		for ; hwm < end; hwm++ {
+			msg := m.queue[hwm]
+
+			if p, ok := m.m[msg.to]; ok {
+				// fmt.Println(i, "S:", m.m[msg.from], msg.signal, "R:", p)
+				p.Pulse(msg)
+			}
+		}
+
+		hwm = 0
+		copy(m.queue, m.queue[end:])
+		m.queue = m.queue[:len(m.queue)-end]
+		// fmt.Println("")
+	}
+}
+func (m *machine) Setup(receivers map[string][]string) {
+	for name, recv := range receivers {
+		if p, ok := m.m[name]; ok {
+			if p, ok := p.(interface{ Receive(...string) }); ok {
+				p.Receive(recv...)
+			}
+		}
+	}
+}
+
+func (m *machine) Stop() {
+	m.stop = true
+}
+
+type IsModule struct {
+	*machine
+}
+
+func (p *IsModule) SetMachine(m *machine) { p.machine = m }
+
+type broadcaster struct {
+	dest []string
+	IsModule
+}
+
+func (b *broadcaster) Pulse(msg message) {
+	b.Send(generate(msg.signal, "broadcaster", b.dest...)...)
+}
+func (b *broadcaster) String() string { return "br" }
+
+type flipflop struct {
+	name  string
+	state signal
+	dest  []string
+
+	IsModule
+}
+
+func (b *flipflop) Pulse(msg message) {
+	if !msg.signal {
+		b.state = !b.state
+		b.Send(generate(b.state, b.name, b.dest...)...)
+	}
+}
+func (b *flipflop) String() string {
+	return fmt.Sprintf("%s(%v)", b.name, b.state)
+}
+
+type conjuction struct {
+	name  string
+	state map[string]signal
+	dest  []string
+
+	pushes map[string][]int
+	activate []int
+	last map[string]int
+	max  map[string]int
+	lcm  int
+
+	IsModule
+}
+
+func (b *conjuction) Receive(names ...string) {
+	if b.state == nil {
+		b.state = make(map[string]signal)
+		b.last = make(map[string]int)
+		b.max = make(map[string]int)
+		b.pushes = make(map[string][]int)
+	}
+	for _, name := range names {
+		b.state[name] = false
+		b.max[name] = int(^uint(0)>>1)
+		b.pushes[name] = []int{}
+
+	}
+}
+func (b *conjuction) Pulse(msg message) {
+	if b.state == nil {
+		b.state = make(map[string]signal)
+		b.last = make(map[string]int)
+		b.max = make(map[string]int)
+	}
+
+	b.state[msg.from] = msg.signal
+
+	if msg.signal {
+		b.pushes[msg.from] = append(b.pushes[msg.from], b.press)
+		b.last[msg.from] = b.press - b.last[msg.from]
+
+
+		// vals := maps.Values(b.max)
+		// if aoc.Min(vals[0], vals...) != 0 {
+		// 	if lcm := aoc.LCM(vals...); lcm > 0 {
+		// 		fmt.Printf("\nfound loop %s = %d %v\n", b.name, lcm, vals)
+		// 	}
+		// }
+	}
+
+	if all(HIGH, maps.Values(b.state)...) {
+		b.activate = append(b.activate, b.press)
+		b.Send(generate(LOW, b.name, b.dest...)...)
+		return
+	}
+	b.Send(generate(HIGH, b.name, b.dest...)...)
+}
+func (b *conjuction) String() string {
+	return fmt.Sprintf("%s(%v)", b.name, b.state)
+}
+
+type rx struct {
+	IsModule
+}
+
+func (rx *rx) Pulse(msg message) {
+	if !msg.signal {
+		panic("pulse received")
+	}
+}
+func (rx *rx) String() string { return "rx" }
+
+func all[T ~int|~bool](match T, lis ...T) bool {
+	if len(lis) == 0 {
+		return true
+	}
+
+	for _, b := range lis {
+		if b != match {
+			return false
+		}
+	}
+
+	return true
+}
+func generate(t signal, from string, destinations ...string) []message {
+	msgs := make([]message, len(destinations))
+	for i, to := range destinations {
+		msgs[i] = message{signal: t, from: from, to: to}
+	}
+	return msgs
+}
+
+func in(n string, haystack []string) bool {
+	for _, h := range haystack {
+		if n == h {
+			return true
+		}
+	}
+	return false
+}
+
+func makeHistory(in []int) [][]int {
+	var history [][]int
+	history = append(history, in)
+
+	for {
+		var diffs []int
+		
+
+		current := history[len(history)-1]
+		if len(current) == 0 { return nil }
+
+		for i := range current[1:] {
+			diffs = append(diffs, current[i+1]-current[i])
+		}
+
+		history = append(history, diffs)
+
+		if len(diffs) == 0 || aoc.Max(diffs[0], diffs[1:]...) == 0 && aoc.Min(diffs[0], diffs[1:]...) == 0 {
+			break
+		}
+	}
+	return history
 }
diff --git a/day20/main_test.go b/day20/main_test.go
index b55d509..8af5bb6 100644
--- a/day20/main_test.go
+++ b/day20/main_test.go
@@ -10,21 +10,36 @@ import (
 	"github.com/matryer/is"
 )
 
-//go:embed example.txt
-var example []byte
+//go:embed example1.txt
+var example1 []byte
+
+//go:embed example2.txt
+var example2 []byte
 
 //go:embed input.txt
 var input []byte
 
-func TestExample(t *testing.T) {
+func TestExample1(t *testing.T) {
 	is := is.New(t)
-	scan := bufio.NewScanner(bytes.NewReader(example))
+	scan := bufio.NewScanner(bytes.NewReader(example1))
 
 	result, err := run(scan)
 	is.NoErr(err)
 
 	t.Log(result)
-	is.Equal(result.valuePT1, 0)
+	is.Equal(result.valuePT1, 32000000)
+	is.Equal(result.valuePT2, 0)
+}
+
+func TestExample2(t *testing.T) {
+	is := is.New(t)
+	scan := bufio.NewScanner(bytes.NewReader(example2))
+
+	result, err := run(scan)
+	is.NoErr(err)
+
+	t.Log(result)
+	is.Equal(result.valuePT1, 11687500)
 	is.Equal(result.valuePT2, 0)
 }
 
@@ -36,6 +51,6 @@ func TestSolution(t *testing.T) {
 	is.NoErr(err)
 
 	t.Log(result)
-	is.Equal(result.valuePT1, 0)
+	is.Equal(result.valuePT1, 819397964)
 	is.Equal(result.valuePT2, 0)
 }