diff --git a/scripts/GameField.gd b/scripts/GameField.gd
index 1e0d559..2cb6a3a 100644
--- a/scripts/GameField.gd
+++ b/scripts/GameField.gd
@@ -280,14 +280,23 @@ func _input(event: InputEvent) -> void:
 var undo_stack = []
 var undo_preview_pos := 0 setget set_undo_preview_pos
 
+func apply_undo_preview():
+	undo_stack.resize(len(undo_stack)-undo_preview_pos)
+	undo_preview_pos = 0
+
 func do_action(action):
+	if undo_preview_pos > 0:
+		apply_undo_preview()
 	action.activate()
 	undo_stack.append(action)
 
 func undo():
 	if !undo_stack.empty():
-		var action = undo_stack.pop_back()
-		action.undo()
+		if undo_preview_pos > 0:
+			apply_undo_preview()
+		else:
+			var action = undo_stack.pop_back()
+			action.undo()
 
 func set_undo_preview_pos(value):
 	if value < 0:  # Negative is past the end of the stack
@@ -300,10 +309,10 @@ func set_undo_preview_pos(value):
 	var delta = value - old_pos
 	if delta > 0:  # We are undoing
 		for i in delta:
-			undo_stack[-old_pos-i].undo()
+			undo_stack[-old_pos-1-i].undo()
 	elif delta < 0:  # We are redoing
 		for i in -delta:
-			undo_stack[-old_pos+1+i].activate()
+			undo_stack[-old_pos+i].activate()
 
 class UndoAction:
 	var action_type