As you roam the ruins of Capital City, the environment will change with each aftershock that hits the city. Buildings will tumble and block paths and catwalks will fall. Blocked paths are the least of your worries, since each time an aftershock hits, you have to find a safe spot and assume a 'safe' posture. However, finding a safe spot is easier said than done. At first glance nearly anything could be considered a safe spot, but running under an overpass or into a building may not always be the smartest option. As you try to escape the city, you have to constantly be on the look out for water in order to maintain your health. Sometimes you'll get lucky and find an undamaged faucet, but most of the time you'll have to pillage and loot stores or find other sources. Adding to the game's more realistic tilt, the space in your backpack is limited - forcing you to pick and choose what you put in it. For example, you'll be very tempted to load that sucker down with water bottles, but then you're likely to not have space for other tools you'll find.
When it comes to tools, the game has a very McGyver-like quality to it. Everything you find can be used in some fashion, it's just up to you to figure out what that use is. Some will be obvious like rope, but others will require a little ingenuity to find their uses and may need to be combined with something else in order to do their job.