===================================================================
--- original.js
+++ change.js
@@ -176,17 +176,21 @@
 	self.collide = collide;
 	self.touch = touch;
 	;
 	function build(name, xAnchor, yAnchor, variations) {
-		var nameVariant = !variations || variations <= 1 ? '' : 1 + Math.floor(Math.random() * variations);
-		var boxGraphics = self.createAsset(name + nameVariant + 'Box', 'Box graphics', xAnchor, yAnchor);
+		var boxGraphics;
+		if (name) {
+			var nameVariant = !variations || variations <= 1 ? '' : 1 + Math.floor(Math.random() * variations);
+			boxGraphics = self.createAsset(name + nameVariant + 'Box', 'Box graphics', xAnchor, yAnchor);
+		}
 		var shadowGraphics = self.createAsset('shadow', 'Shadow image', 0.5, 0.5);
 		var hitboxGraphics = self.createAsset('hitbox', 'Hitbox graphics', .5, .25);
 		shadowGraphics.alpha = 0.5;
 		shadowGraphics.y = -BOX_HEIGHT * 0.5;
 		hitboxGraphics.width = BOX_WIDTH * 0.9;
 		hitboxGraphics.height = BOX_HEIGHT * 0.6;
 		hitboxGraphics.alpha = 0;
+		self.graphic = boxGraphics;
 		self.hitbox = hitboxGraphics;
 		self.shadow = shadowGraphics;
 	}
 	function update(args) {
@@ -315,9 +319,9 @@
 	function activation(args) {
 		if (countdown <= 0) {
 			explode(args);
 		} else if (countdown % 20 === 0) {
-			LK.effects.flashObject(self, 0xff0000, 500);
+			LK.effects.flashObject(self.graphic, 0xff0000, 500);
 		}
 		countdown--;
 	}
 	function collide(args) {
@@ -358,9 +362,9 @@
 						if (box.y > min) {
 							if (box !== self) {
 								if (box instanceof TntBox) {
 									box.active = true;
-								} else if (!(box instanceof StoneBox)) {
+								} else if (!(box instanceof StoneBox || box instanceof InvisBox)) {
 									box.alive = false;
 								}
 							}
 						} else {
@@ -373,13 +377,10 @@
 	}
 });
 var Column = Container.expand(function (x, y, index) {
 	var self = Container.call(this);
-	var boxes = [];
+	var boxes = [self.add(new InvisBox(0, STAGE_HEIGHT - FLOOR_OFFSET))];
 	var countdown = SPAWN_INITIAL + getCountdown();
-	var shadowGraphics = self.createAsset('shadow', 'Shadow image', 0.5, 0.5);
-	shadowGraphics.alpha = 0.5;
-	shadowGraphics.y = STAGE_HEIGHT - FLOOR_OFFSET;
 	;
 	self.x = x;
 	self.y = y;
 	self.boxes = boxes;
@@ -414,15 +415,8 @@
 			}
 		}
 	}
 	function update(args) {
-		var upperBox = boxes[0];
-		var shadowVisible = upperBox && upperBox.falling;
-		shadowGraphics.visible = shadowVisible;
-		if (shadowVisible) {
-			var scale = 1 - (STAGE_HEIGHT - FLOOR_OFFSET - upperBox.y) / STAGE_HEIGHT;
-			shadowGraphics.scale.set(scale);
-		}
 		if (--countdown <= 0) {
 			countdown = getCountdown();
 			if (self.count < COLUMN_VOLUME) {
 				var {boxList, game} = args;
@@ -446,13 +440,11 @@
 			}
 		}
 	}
 });
-var Player = Container.expand(function (x, y) {
-	var self = Container.call(this);
-	self.x = x;
-	self.y = y;
-	;
+var Player = ShiftableContainer.expand(function (x, y) {
+	var self = ShiftableContainer.call(this);
+	var baseShiftContainer = self.shiftContainer;
 	var isJumping = false;
 	var verticalSpeed = 0;
 	var floorHeight = y;
 	var targetColumn = Math.floor(x / BOX_WIDTH);
@@ -463,15 +455,18 @@
 	hitboxGraphics.width = PLAYER_SIZE * 0.6;
 	hitboxGraphics.height = PLAYER_SIZE * 0.8;
 	hitboxGraphics.alpha = 0;
 	;
+	self.x = x;
+	self.y = y;
 	self.heightClimbed = 0;
 	self.invulnerability = 0;
 	self.airborne = false;
 	self.hitbox = hitboxGraphics;
 	self.move = move;
 	self.jump = jump;
 	self.update = update;
+	self.shiftContainer = shiftContainer;
 	;
 	function getColIndex() {
 		return Math.floor(self.x / BOX_WIDTH);
 	}
@@ -539,16 +534,31 @@
 				newColIndex = colIndex;
 			}
 		}
 		if (!self.airborne) {
+			var heightIndex = Math.round(self.heightClimbed / BOX_HEIGHT);
 			columnList[newColIndex].touch(self, rowIndex - 1);
-			if (rowIndex > self.heightClimbed) {
-				interface.increment((newRowIndex - self.heightClimbed) * POINTS_GAIN_CLIMBING);
-				self.heightClimbed = rowIndex;
+			if (rowIndex > heightIndex) {
+				interface.increment((newRowIndex - heightIndex) * POINTS_GAIN_CLIMBING);
+				self.heightClimbed = newRowIndex * BOX_HEIGHT;
+				if (heightIndex >= SHIFT_THRESHOLD) {
+					return true;
+				}
 			}
 		}
+		return false;
 	}
+	function shiftContainer(amount) {
+		baseShiftContainer(amount);
+		;
+		self.heightClimbed -= amount;
+	}
 });
+var InvisBox = Box.expand(function (x, y, args) {
+	var self = Box.call(this, x, y, args);
+	;
+	self.build();
+});
 ;
 var STAGE_WIDTH = 2048;
 var STAGE_HEIGHT = 2732;
 var STAGE_TICKS = 60;
@@ -575,9 +585,9 @@
 var INVULNERABILITY_TIME = 5 * STAGE_TICKS;
 var INSTRUCTION_DURATION = 5 * STAGE_TICKS;
 var SHIFT_THRESHOLD = 6;
 var SHIFT_COUNT = 3;
-var SHIFT_DURATION = STAGE_TICKS / 2;
+var SHIFT_DURATION = STAGE_TICKS / 3;
 var SHIFT_AMOUNT = SHIFT_COUNT * BOX_HEIGHT / SHIFT_DURATION;
 var BOX_SPEED = 5;
 var BOX_GRAVITY = 0.2;
 var TNT_COUNTDOWN = 2 * STAGE_TICKS;
@@ -641,10 +651,10 @@
 	LK.on('tick', function () {
 		if (interface.isGameOver) {
 			interface.gameOver();
 		} else if (interface.isPaused = shiftTicks > 0) {
-			shiftTicks--;
 			var containers = [[background, floor, player], boxList, effectList];
+			shiftTicks--;
 			containers.forEach(function (subContainers) {
 				subContainers.forEach(function (container) {
 					container.shiftContainer(SHIFT_AMOUNT);
 				});
@@ -653,9 +663,11 @@
 			var playerArgs = {
 				interface,
 				columnList
 			};
-			player.update(playerArgs);
+			if (player.update(playerArgs)) {
+				shiftTicks += SHIFT_DURATION;
+			}
 			;
 			var columnArgs = {
 				game: self,
 				boxList