There really aren’t any nuances to Mega Mall Story. I found it fun for one play. The second time it was terribly easy because I’d researched all the shops and unlocked all the combos. It’s really dumb that research carries over from game to game, except for a few key milestone shops. I guess that feature is for the “push button to win” crowd.
Though the game claims otherwise, facilities (i.e. vending machines) don’t earn any money at all, except in the very early game when customers have almost no choices. However, they do act as a boost to all shops on the same floor, and they’re often part of combos. Since facilities don’t generate any income, it’s OK to build multiple copies on different floors if you feel you need the boost.
In the early game, you can ignore combos because you can’t build any, and you don’t want any duplicate shops, period. Essentially you should just look over your list of customers, and see what shops they want. If you build that shop and the customer visits it, they’ll become a regular and start spending a lot more. Most of them will want shops you can’t build yet.
Investments in the 3 non-mall areas, such as houses, aren’t investments per se since they don’t return anything. Rather, you’re buying new customers. Every time you build something, you’ll get one or more new customers who will visit the mall and hopefully become regulars.
Shops have a preferred floor range. I.e. some shops work best on the 1st-4th floors, some on the 5th-10th, etc. I’ve forgotten the precise ranges, but they’re pretty broad. All bonuses are clear once you get them because examining the shop details tells you what bonuses apply. Preferred floor is useful until your mall is big enough for combos, at which point the combo bonuses overshadow the preferred location bonus.
In the mid game, once you’ve expanded the mall horizontally at least once, the game is all about combos. Just look over the list and build shops next to each other, which will boost both popularity and quality of all the shops involved. Facilities in combos get a boost that affects all shops on the same floor. When you’ve expanded horizontally twice, combos with nothing but facilities can be very powerful.
A handful of shops are part of multiple combos. This is the only remotely complicated part of the game, figuring out how to build two combos by placing 5 shops adjacent in the correct order. The overlapping store gets the bonus from both combos. If the overlapping item is a facility, that can end up boosting everything on the floor.
Once you’ve got a fair sized mall, you can stop looking at customer preferences. Someone is going to want any shop you build, once you have enough people coming.
Sales are a late game thing. They’re a way of converting hearts into cash, and generally you want to spend all your hearts on research and shop upgrades. They don’t actually reduce prices at all, they just increase a store’s popularity for a month. A sale can boost the income of a very high-priced endgame shop like the planetarium or casino through the roof.
