Jump from exploration into combat
Games started with this ages ago, especially RPGs. Run into an enemy and suddenly you have a change in surroundings, controls and your team members appear out of nowhere.
It started out as a limitation of the hardware but limitations often spark creativity. There are benefits to keep things separate. Game design can go completely wild and creative because nothing that happens in the "combat dimension" upsets the "outer world". Just think about jumping attacks that catapult you 50 m into the air. Or firing your "Meteor Storm" spell in a small wooden hut.
A prominent example for creative use is the Final Fantasy series. Once the battle begins, you zoom into the action. Backgrounds, enemies and heroes are presented with much more detail than would be possible in the "outer world". Spells and skills get much more "juicy" animations.
|Typical combat situation in Final Fantasy 6|
The middle way: make it less obvious
Gamers are well accustomed to this transition thing and it rarely becomes a point of criticism. Still, it may break immersion. Therefore, much effort has been put into ideas to smoothen this transition. Small and subtle things like displaying your party members following your avatar while you run around.Or they abolish the battle backgrounds and place the heroes directly in the area you were running around.
The priciples above are executed fairly well in the game Septerra Core.
|Septerra Core exploration|
|Septerra Core combat|
The smoothest transition is no transition
From a player´s point of view, it is most natural when there is no separate combat screen. You take on your foes in the same place you were exploring just a few seconds ago. This can be considered the most elegant solution but it can pose a big challenge for a game developer. By keeping the processes as isolated as possible, it is much easier to assure that they work without interacting, conflicting and create bugs. It is like mixing your 2 favourite breakfast cereals. It may taste good but if not, picking the mixture apart if something is not working out can be an unnerving task. So congratulations if a game developer can pull it through without plastering his game with bugs.
Blending exploration, combat and many cool abilities that are primarily designed for puzzle solving but can also be helpful in battle is one of the defining traits of the Zelda franchise. (A short and entertaining video review of "A Link between Worlds" can be found in ProJared´s channel.)