range from fighting with an axe, to bartering, to picking locks. By participating in combat, quests and exploration, the character gains experience points. When certain amounts of experience points are accumulated, the character levels up, gaining additional hit points and mana. Experience is required to recite mantras at shrines in the game. Each mantra is a statement—such as "Om Cah"—that increases proficiency in a specific skill when typed. Simple mantras are provided in the game's manual, while more complex ones are hidden throughout the game. An inventory on the HUD lists the items and weapons carried by the player character; capacity is limited by weight. Players equip items via a paper doll system, wherein items are clicked-and-dragged onto a representation of the player character. Combat occurs in real-time, and the player character may use both melee and ranged weapons. The player attacks by holding the cursor over the game screen and clicking, depressing the button longer to inflict greater damage. Some weapons allow for different types of attacks depending on where the cursor is held; for example, clicking near the bottom of the screen may result in a jab, while clicking in the middle produces a slash. Simulated dice rolls occur behind the scenes to determine weapon accuracy. Enemies sometimes try to escape when near death, and the game's stealth mechanics may occasionally be used to avoid combat altogether. The player may cast spells by selecting an appropriate combination of runestones. Like mantras, runestones must be found in the game world before use. There are over forty spells, some undocumented; their effects range from causing earthquakes to flight. The developers intended Ultima Underworld to be a realistic and interactive "dungeon simulation", rather than a straightforward role-playing video game. For example, many objects in the game have no actual use, while a lit torch may be used on corn to create popcorn. Weapons deteriorate with use, and the player character must eat and rest; light sources burn out unless extinguished before sleeping. A physics system allows, among other things, for items to bounce when thrown against surfaces. The game contains non-player characters (NPCs) with whom the player may interact by selecting dialogue choices from a menu. Most NPCs have possessions, and are willing to trade them. The game was designed to give players "a palette of strategies" with which to approach situations, and its simulation systems allow for emergent gameplay. Plot