Oxygen is essential for your duplicates. Pay attention to its concentration in places where your people will work. If it starts to run out, they will hold their breath and they will continue working without oxygen for a short time and then they will run to the nearest place with oxygen to replenish its supply. The larger the blue glow in the room, the more oxygen there is. You can also hover over a given field, in order to see how much oxygen there is.
Gas flow. This is a very important factor while building a base, you will find more detailed information later on in the guide. Remember, that oxygen usually rises and carbon dioxide, which is exhaled by your colonists, falls downwards or into the bottom right-hand corner. This means that if you dig down, your people will be more exposed to the lack of oxygen than when digging up. It would also be better to place the bedrooms in the middle or upper part of the base than at the very bottom. Use the oxygen overlay to quickly figure out the situation.
Take care of the food supply by growing crops. Remember that plants require a sufficient amount of air to properly grow. Lack, or even insufficient amount of gases in the environment will halt their growth. Each plant species prefers different temperature ranges, and you need to be aware of them when planting a specific crop. Some of them will require warm environment, some other - a cold one.
Your duplicates can climb up to 1 or 2 fields and jump one field. Remember this when expanding your base. You will be able to receive new people from time to time, which will be indicated by the appropriate information and glow around your starting object - the Printing Pod.
When it comes to digging, watch out for sand tiles, as they can fall as you dig other materials from underneath them. Additionally, your characters can dig up to two tiles away from their position. The same principle applies to pumping water.
Be careful when digging near water tanks. Each mineral has its own resistance to water pressure. If you dig a long tunnel just one tile away from water, the rock can start to burst and water will flood your base. Not only can it drown your colonists (thankfully it does not happen instantly), but it also prevents you from using multiple machines in your base. It will be the most difficult for you to get rid of water at the beginning of the game, when you do not have the proper equipment to remove excess water.
The first object to build is the outhouse! Seriously, you do not want your base flooded by the physiological secretions of your duplicates. Not only does this affect the decor factor, but it also increases the stress level and the generated contaminated water also produces contaminated oxygen. Only drawbacks.
If a duplicate dies at the beginning of the game, bury his body. Otherwise, his corpse will start to spawn creatures, the Morb, which exhale contaminated oxygen. They are not a direct threat but will make your life difficult. At some point, you will be able to use their skills to your advantage. (See section: Base, Special Rooms, Morb "Farm").
Stress. If a given duplicate reaches 100% in the stress tab, he will start vomit or destroy the environment depending on his behaviour. If he vomits, there will be contaminated water flowing within the base. On the other hand, if he explodes with anger, he will destroy some object or machine in the base, usually the ones most needed, such as the generator or machine needed for the production of oxygen. Take care of the decor of your base and build the appropriate structures, that will reduce stress. Clean air and good food will also have a positive effect on the duplicants.