When you begin to play Castlevania II, you have the option of starting a new game, or continuing a previous game by entering a password. You will receive a new password whenever you lose all of your lives and your game is over.
Simon's Quest takes place in a non-linear world, so you may revisit previous areas at any point in the game. There are certain areas which are blocked off until you find an appropriate item, however much of the world can be explored right from the beginning. Despite the non-linear layout, the plot progression is fairly linear. There are five mansions that must be explored before you can enter the last area, and while you can skip a few of the mansions and come back later, there is no real reason to do so.
While the game does not have explicitly defined chapters or stages, it can be logically broken up into six sections; one for each of the mansions. You start the game in the Town of Jova, with nothing but your leather whip and 50 hearts.
Gameplay basics
Unlike the first game, which was strictly a side-scrolling action game, in Simon's Quest, you may spend as much time exploring as you do fighting. You must travel around the world in search of the five mansions where Dracula's body parts are kept. Along the way you will pass through several towns where you can buy new weapons or items, and get clues from the villagers.
In addition to providing ammunition for some of your special weapons, hearts are the currency of the land. They are found by killing the various enemies that inhabit the mansions, woods, lakes, swamps, and mountains of the land. The merchants are typically found inside buildings, although a few wander the streets. You can hold a maximum of 256 hearts at any time, so don't get hung up on grinding for money beyond that point.
It should be noted that the information provided by villagers is rarely accurate, which may mislead you or cause you to question the validity of what you've been told. Many of the villagers simply enjoy gossip and spreading rumors, while other fear reprisal from Dracula if they are caught assisting you. Still, there are a few brave souls who will dare to defy the Count, and impart useful information. The trouble is, it's difficult to tell who those people are.
Combat
Your basic method of attacking is with the legendary whip known as the Vampire Killer. In addition you have several weapons, such as daggers and holy water. All of the weapons are useful at certain points in the game, and some enemies are easier to defeat with a specific weapon. You have unlimited usage of the basic dagger and the holy water, so you needn't fear running out of hearts when you use them. Other weapons like the two knives, the mystic flame, and the diamond will drain your heart collection, and will not work if you run out of hearts.
Leveling
As with most RPGs, and games with RPG elements, you gain experience points. Unlike most RPGs, you do not gain experience by killing monsters, but rather by collecting the hearts which some of the defeated monsters drop. You earn one less experience point than the number of hearts you collect. Once you have enough experience points, you gain a level and become stronger. However, once you gain a level, easier enemies no longer give you experience, forcing you to forge ahead to more challenging areas in order to continue improving. In Simon's Quest, your level affects the amount of health you have and how much damage you receive from enemies. As you travel into stronger areas, enemies will do progressively more damage to you, so it's important to maintain as high a level as possible. Leveling up does not increase your strength, which can only be upgraded by purchasing or collecting better weapons. You start with a level of 0 and can go no higher than level 6, at which point no enemies will give you experience.
Healing
You can heal yourself, free of charge, at a town's church. Step inside and talk to the priest to be restored. It should be noted that churches are only open during the day, so if it is nighttime and you are severely wounded, simply find a corner to hide in until daybreak.
Should you die, you lose a life and start back at the entrance to the screen, with full health. You do lose all of your experience points, however your level will not get reset. If you lose all of your lives, the game is over, but you can continue by using a password.
One last way to heal is to level up. Any time you level up, whether you gain additional health or not, you will be fully healed instantly.
Day/Night
As time goes by, the game will toggle between day and night. The game will pause to inform you of each transition before the cycle changes. The land itself does not change, but enemies become stronger. Generally speaking, the game is more difficult at night. At night, all shops and churches are closed, and no villagers are on the streets. Towns are no longer safe from monsters as ravens and zombies roam about. Enemies take twice as many hits to die at night. They may drop larger hearts (e.g. enemies which drop small hearts by day will drop half hearts at night. Some enemies which drop half hearts may drop large hearts, but not all do.)
On the clock, day time is from 06:00 to 17:59. Night time is from 18:00 to 05:59. Whenever you start a game (new or from a password), the clock will always be set to 12:00. To check the current time, you can press 
. It will slowly count up as time passes while you are outdoors. If you need it to be day you can hide at the edge of a screen and simply wait for the sun. As long as all enemies are defeated and you don't move, no new ones should appear.
Time does not advance while you are indoors. This includes any building in a town, any of the mansions, and Dracula's Castle.
Passwords
- See the passwords section for a list of example passwords.
A password is constructed from 16 alpha-numeric characters. The game doesn't record your game state and then assign you a password, rather it calculates the game state based on the password you enter. As a result, if you understand how the system works, you can set up the game however you want.
The original version of the game for the Famicom Disk System did not use passwords, instead recording progress directly onto the game disk.