The Heads Up Display, or HUD, is an element that appears in every Kingdom Hearts game. It is almost always at the bottom left corner of the screen - with the exclusion of Kingdom Hearts: Chain of Memories- and details multiple things. However, HP is always present in the HUD.
Mechanics
Kingdom Hearts
Sora's HUD in Kingdom Hearts.
In Kingdom Hearts, the HUD is in the bottom left hand corner. On the very inside of the HUD, there is a picture of Sora which flinches every time damage is taken.
Surrounding the picture are multiple bars that twist around it. The innermost one is called the HP Bar, which, true to its name, details the amount of Hit Points Sora has left. When the HP reaches the Alarm Zone - the area when the HP reaches a critical level and starts flashing red - the picture changes to one of Sora with a blue tint near his hairline, his eyes shadowed.
The next and outermost bar is called the MP Bar. This bar details how much MP Sora has left for casting spells. This is divided into several sections, each one representing 1 MP. Additionally, reddish-orange bars called Charge Points line the outermost area of the MP Bar. When the MP falls below the maximum, these appear when damage is taken - if MP Rage is equipped - or when damage is given to foes. The line extends beyond the MP Bar to the extent of the size of 1 MP; when it goes beyond it, the additional MP reappears and the bar starts over again.