Two bots and basic relay, with rendering

.gitignore

@@ -0,0 +1 @@
+/relay.exe

main.go

@@ -0,0 +1,112 @@
+package main
+
+import (
+	"time"
+
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/imdraw"
+	"github.com/faiface/pixel/pixelgl"
+	"golang.org/x/image/colornames"
+)
+
+func run() {
+	cfg := pixelgl.WindowConfig{
+		Title:  "Relay",
+		Bounds: pixel.R(0, 0, 2048, 512),
+		VSync:  true,
+	}
+
+	w, err := pixelgl.NewWindow(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	s := newState()
+
+	start := time.Now()
+
+	for !w.Closed() {
+		w.Clear(colornames.Peru)
+		s = updateState(s)
+		render(s, w, time.Since(start))
+		w.Update()
+	}
+}
+
+func main() {
+	pixelgl.Run(run)
+}
+
+func render(s state, w *pixelgl.Window, d time.Duration) {
+	b := w.Bounds()
+	i := imdraw.New(nil)
+	offset := b.Size().X / steps
+
+	for _, bot := range s.bots {
+		if bot.active {
+			i.Color = pixel.RGB(0, 1, 0)
+		} else {
+			i.Color = pixel.RGB(1, 0, 0)
+		}
+		from := pixel.V(b.Min.X+25, b.Center().Y)
+		pos := from.Add(pixel.V(float64(bot.pos)*offset, 0))
+
+		i.Push(pos)
+
+		i.Clear()
+		i.Circle(50, 0)
+
+		i.Draw(w)
+	}
+}
+
+type state struct {
+	bots []bot
+}
+
+func newState() state {
+	return state{
+		bots: []bot{
+			{pos: 0, active: true},
+			{pos: steps / 2},
+		},
+	}
+}
+
+type bot struct {
+	pos    int
+	active bool
+}
+
+func updateState(sOld state) state {
+	s := sOld
+
+	for i := range s.bots {
+		updateBot(&s.bots[i], sOld)
+	}
+	return s
+}
+
+func updateBot(b *bot, s state) {
+	if !b.active {
+		return
+	}
+
+	b.pos++
+	maybePassBaton(b, s)
+}
+
+func maybePassBaton(b *bot, s state) {
+	for i, bb := range s.bots {
+		if b.pos == bb.pos {
+			continue // same bot
+		}
+		if bb.pos-b.pos == 1 {
+			b.active = false
+			s.bots[i].active = true
+			return
+		}
+	}
+}
+
+const steps = 500