"I had the Roller Coaster as a Christmas present and have been enjoying building it over the past 8 days. The attention to detail is great and building all the gear mechanism needs plenty of attention, but the results are worth it! Thanks to a previous reviewer (Valerian70) I was able to quickly solve the problem with the bumpers at the top that were moving the wrong way. On page 169 of the first booklet the position of the small cream cog in action 163 needs to be facing inwards on the other side of the first cog. This will make the bumpers turn correctly to keep the cars moving round the highest point when they reach the top of the long chain slope. Once corrected everything ran smoothly."