diff --git a/internal/math/vec.go b/internal/math/vec.go
index 0b439ee..8f23fdd 100644
--- a/internal/math/vec.go
+++ b/internal/math/vec.go
@@ -24,3 +24,21 @@ func (v *Vec) UnmarshalJSON(b []byte) error {
 }
 
 func (v Vec) Add(v2 Vec) Vec { return Vec{v.X + v2.X, v.Y + v2.Y} }
+
+func (v Vec) Unit() Vec {
+	var out Vec
+	switch {
+	case v.X < 0:
+		out.X = -1
+	case v.X > 0:
+		out.X = 1
+	}
+
+	switch {
+	case v.Y < 0:
+		out.Y = -1
+	case v.Y > 0:
+		out.Y = 1
+	}
+	return out
+}
diff --git a/internal/server/session.go b/internal/server/session.go
index bd619a5..ae9d273 100644
--- a/internal/server/session.go
+++ b/internal/server/session.go
@@ -86,7 +86,7 @@ func (sn *session) read() {
 			var req wire.Request
 			if err := json.Unmarshal(b, &req); err != nil {
 				sn.Error("unable to parse request: %v", err)
-				sn.outbox <- wire.ErrorResponse(0, "unable to parse request: %v", err)
+				sn.outbox <- wire.ErrorResponse(req.Seq, "unable to parse request: %v", err)
 				break
 			}
 			sn.Info("received message of type %T", req.Body)
diff --git a/internal/server/sim/player.go b/internal/server/sim/player.go
index cb9b9b1..fde03ee 100644
--- a/internal/server/sim/player.go
+++ b/internal/server/sim/player.go
@@ -12,7 +12,7 @@ type player struct {
 	*room
 	name    string
 	outbox  chan wire.Response
-	pending []Request
+	pending *Request
 	avatar  *entity
 }
 
@@ -70,14 +70,13 @@ func (s *SpawnPlayer) exec(r *room, p *player, seq int) result {
 			behavior: doNothing{},
 		}
 		p := &player{
-			Log:     r.Log.Child("players").Child(s.Name),
-			room:    r,
-			name:    s.Name,
-			outbox:  s.Outbox,
-			pending: make([]Request, 0, 32),
-			avatar:  avatar,
+			Log:    r.Log.Child("players").Child(s.Name),
+			room:   r,
+			name:   s.Name,
+			outbox: s.Outbox,
+			avatar: avatar,
 		}
-		p.pending = append(p.pending, Request{Seq: seq, From: s.Name, Wants: s})
+		p.pending = &Request{Seq: seq, From: s.Name, Wants: s}
 		r.players[s.Name] = p
 		r.tiles[0].here = p.avatar
 		s.queued = true
diff --git a/internal/server/sim/room.go b/internal/server/sim/room.go
index 912358e..adb66e7 100644
--- a/internal/server/sim/room.go
+++ b/internal/server/sim/room.go
@@ -19,19 +19,22 @@ type room struct {
 
 func (r *room) update(dt time.Duration) {
 	for _, p := range r.players {
-		for _, req := range p.pending {
-			res := req.Wants.exec(r, p, req.Seq)
-			p.outbox <- wire.Response{Re: req.Seq, Body: res.reply}
-			if res.announce != nil {
-				for _, p2 := range r.players {
-					if p2 == p {
-						continue
-					}
-					p2.outbox <- wire.Response{Body: res.announce}
+		if p.pending == nil {
+			continue
+		}
+		req := p.pending
+		p.pending = nil
+
+		res := req.Wants.exec(r, p, req.Seq)
+		p.outbox <- wire.Response{Re: req.Seq, Body: res.reply}
+		if res.announce != nil {
+			for _, p2 := range r.players {
+				if p2 == p {
+					continue
 				}
+				p2.outbox <- wire.Response{Body: res.announce}
 			}
 		}
-		p.pending = p.pending[0:0]
 	}
 
 	for _, t := range r.tiles {
diff --git a/internal/server/sim/world.go b/internal/server/sim/world.go
index 3bddc5c..e0311a8 100644
--- a/internal/server/sim/world.go
+++ b/internal/server/sim/world.go
@@ -78,7 +78,11 @@ func (w *World) Run(hz int) {
 				w.Error("received non login request of type %T from unknown player %q", req.Wants, req.From)
 			}
 
-			p.pending = append(p.pending, req)
+			if p.pending == nil {
+				p.pending = &req
+			} else {
+				p.outbox <- wire.ErrorResponse(req.Seq, "you already have a request for this frame")
+			}
 
 		case <-ticker.C:
 			w.tick(time.Since(lastTick))