WASD moves the protagonist on an isometric area, while the mouse button is used to interact.
Castaway is an adventure game set on a strange island. The protagonist wakes up on a beach and has to find out where he is and what has to be done. Castaway is an action RPG utilizing both mouse and keyboard.
The battle system of Castaway can be compared to adventure games that use a point-and-click interface like Diablo. Click an enemy and the protagonist will start to attack it until you move him or the creature dies. Items can be picked up by clicking on them and your inventory can be accessed by clicking the bag icon. Castaway is heavily mouse-based on everything outside of movement.
Killing enemies gives both drops and EXP. When you gain enough EXP, you gain a level granting access to better equipment, increasing stats, and HP. Further progressions in power are gained by doing quests which grants new abilities and methods of dispatching increasingly stronger foes that inhabit the island.
An important aspect of the game is pets. A pet is exactly what you expect it to be in adventure games. Pets in Castaway will back you up in battle, and you can only have one active pet at a time. The one you get at the start is one of a kind so be nice to it.
Shortly after beginning you will reach the titular town Castaway. Here you can save your game, buy (expensive) equipment, learn magic, and take on quests for the local villagers. A place of note is the Pet Center. When you find eggs, you can place them in the Egg Hatchery and leave the eggs alone until they hatch. You can also choose what pet to take with you on your journeys. In general, high-level pets gain stats better than low-level pets, so don't get too attached to one pet because he'll become obsolete eventually.
Do quests, kill monsters, discover the secrets of the island.
Damage can vary quite wildly, if you feel your health is low, retreat as quickly as you can to avoid losing your progress.
Quests may not seem to give an awful lot, but those rewards add up. Quests available are based on your level and progress.
Beetles drop fire shards and eggs, use these for more pets and spells.
Death is permanent in Castaway, if your pet dies, that's it. Don't get too cocky in a fight.