My son has been re-playing through the Lego games on the 360 lately by himself and occasionally calls me into his room for help saying "I'm stuck!" or "I don't know what to do next!" Even though I'm looking at a mid point of the level, it's generally easy to figure out how to help him in the level with a little investigation.

There are times where the scenario is a little more complicated, but these are just opportunities for me to put on my Designer's Hat and think through what the intended flow of the level is.  I sometimes need to take the controller for a minute and walk around looking at which of the mechanics have been used up to this point and look closely at what tools are available to the player currently.  I find it's a really fun and sometimes challenging exercise that helps me to think more carefully as I'm planning out the levels that I build professionally.

I also find that these are good teaching opportunities for my son.  So, I will usually have him show me where he is currently and then talk me through all of the steps he took to get there.  Once he's done this, I talk to him about which mechanics are available to him and what of those things he might have done that freed up the next move.  I was looking at a Lego Batman level and he hadn't yet realized that when he lowered a bridge that he needed to run back off screen a bit to grab the vehicle that was at the first part of the area.  When he told me the bridge came down I asked him what he thought the bridge might be used for and the light went off and he ran back for the vehicle.

All of this is possible because of how well the Lego games nail down simple solid mechanics and then repeat them in various ways throughout the levels.  Careful thought and planning has to go into layout out levels of this type since the player is generally forced to rely on analytical thought to figure out solutions.  In any level you are building, it is an interesting exercise to take a look at a mid point and decide how easy it is for a confused player to figure out their next steps.