diff --git a/js/defs.js b/js/defs.js
index 5f54e20..d1bb0dd 100644
--- a/js/defs.js
+++ b/js/defs.js
@@ -183,15 +183,14 @@ export const COMPAT_FLAGS = [
     key: 'force_lynx_animation_lengths',
     label: "Animations use Lynx duration",
     rulesets: new Set(['lynx']),
+}, {
+    key: 'actors_move_instantly',
+    label: "Movement happens instantly",
+    rulesets: new Set(['ms']),
 },
 
 // Tiles
 {
-    // XXX this is goofy
-    key: 'tiles_react_instantly',
-    label: "Tiles react when approached",
-    rulesets: new Set(['ms']),
-}, {
     key: 'rff_actually_random',
     label: "Random force floors are actually random",
     rulesets: new Set(['ms']),
diff --git a/js/game.js b/js/game.js
index c5b0963..65a3d0d 100644
--- a/js/game.js
+++ b/js/game.js
@@ -33,7 +33,7 @@ export class Tile {
 
     // Gives the effective position of an actor in motion, given smooth scrolling
     visual_position(update_progress = 0, update_rate = 0) {
-        if (! this.previous_cell || this.movement_speed === null) {
+        if (! this.previous_cell || this.movement_speed === null || this.moves_instantly) {
             return [this.cell.x, this.cell.y];
         }
 
@@ -414,6 +414,9 @@ export class Level extends LevelInterface {
                     }
                     if (tile.type.is_actor) {
                         this.actors.push(tile);
+                        if (this.compat.actors_move_instantly) {
+                            tile.moves_instantly = true;
+                        }
                     }
                     cell._add(tile);
 
@@ -564,7 +567,7 @@ export class Level extends LevelInterface {
             // but it can't anyway because Tile.wire_directions = 0; need some
             // other way to identify a tile as wired, or at least an actor
             if (actor && actor.wire_directions &&
-                (actor.movement_cooldown === 0 || this.compat.tiles_react_instantly))
+                (actor.movement_cooldown === 0 || this.compat.actors_move_instantly))
             {
                 wire_directions = actor.wire_directions;
             }
@@ -1128,7 +1131,7 @@ export class Level extends LevelInterface {
                 }
             }
 
-            if (! this.compat.tiles_react_instantly) {
+            if (! this.compat.actors_move_instantly) {
                 this.step_on_cell(actor, actor.cell);
             }
             // Note that we don't erase the movement bookkeeping until next decision phase, because
@@ -1971,7 +1974,7 @@ export class Level extends LevelInterface {
             this.add_tile(actor, goal_cell);
         }
 
-        if (this.compat.tiles_react_instantly) {
+        if (this.compat.actors_move_instantly) {
             this.step_on_cell(actor, actor.cell);
         }
     }
@@ -2198,6 +2201,9 @@ export class Level extends LevelInterface {
                 }
                 if (tile.cell) {
                     this.add_actor(tile);
+                    if (this.compat.actors_move_instantly) {
+                        tile.moves_instantly = true;
+                    }
                 }
                 this.add_tile(dropping_actor, cell);
             }
diff --git a/js/main.js b/js/main.js
index eefa27a..2113d57 100644
--- a/js/main.js
+++ b/js/main.js
@@ -1750,7 +1750,6 @@ class Player extends PrimaryView {
         else {
             // Figure out how far we are between the last game update and the next one, so the
             // renderer can interpolate appropriately.
-            let now = performance.now();
             let elapsed = (performance.now() - this.last_advance) / 1000;
             let speed = this.play_speed;
             if (this.state === 'rewinding') {