Zelda II: The Adventure of Link (Trax's disassembly and the USA ROM)

A new game starts with four heart containers and four magic containers. Picking up a container adds one, and a full meter holds 32 units per container less one, so four containers fill to 127. zelda2/containers

About: Zelda II: The Adventure of Link Health upgrade

{
 "start": 4,
 "unitsPerContainer": 32
}

The comment's "20" is hexadecimal. A byte meter can't hold more than eight containers' worth (8 × 32 − 1 = 255).

Cited by: Health upgrade, Magic meter, Zelda II: The Adventure of Link

A monster's damage code (0–7) and Link's life level (1–8) pick the life a hit takes from an 8 × 8 table, halved while the Shield spell is on. Code 0 takes 16 units at life level 1 and 4 at level 8; code 6 takes 224 and 80; code 7 takes 255 at every level. zelda2/damage-table

About: Zelda II: The Adventure of Link Damage formula

{
 "code0": [
  16,
  12,
  12,
  12,
  8,
  4,
  4,
  4
 ],
 "code3": [
  96,
  72,
  56,
  48,
  40,
  32,
  28,
  24
 ],
 "code6": [
  224,
  192,
  160,
  144,
  128,
  112,
  96,
  80
 ],
 "code7": 255
}

The damage code is the low nibble of the monster's vulnerability byte (L5426-L5427). Life levels are bought with experience, so this is the game's defense stat.

Cited by: Zelda II: The Adventure of Link

A sword hit takes 2, 3, 4, 6, 9, 12, 18, or 24 hit points from a monster for attack levels 1 to 8, and the Thunder spell's entry is 50. zelda2/attack-power

About: Zelda II: The Adventure of Link Damage formula

[
 2,
 3,
 4,
 6,
 9,
 12,
 18,
 24
]

Cited by: Zelda II: The Adventure of Link

A hit sets Link's immunity timer to 4 and his injured timer to 32. The game counts the injured timer down every frame but the immunity timer only once every 21 frames, so the immunity lasts 64 to 84 frames, depending on where in the cycle the hit lands. zelda2/hurt-timers

About: Zelda II: The Adventure of Link Invincibility frames

{
 "immunity": 4,
 "tickFrames": 21,
 "injured": 32
}

The hit routine returns without damage while $0518 is above 0 (L5430-L5431). The loop doesn't run during dialogs.

Cited by: Zelda II: The Adventure of Link

A monster's body hit sets Link's horizontal speed from a table, $0D or $F3 (−13) by the comments for facing left or right, and his vertical speed to $FE (−2), a hop away. zelda2/recoil

About: Zelda II: The Adventure of Link Knockback

{
 "x": 13,
 "y": -2
}

Which side maps to which sign is the comments' reading; the code picks the entry from bank7_Determine_Enemy_Facing_Direction_relative_to_Link, not read here. The units of $70 aren't established.

Cited by: Zelda II: The Adventure of Link

A spell's cost comes from an 8 × 8 table by spell and magic level, in meter units (32 per container). Shield costs 64 at magic level 1 and 32 from level 4; Life costs 140 at level 1 and 100 from level 5; Thunder costs 240 until level 7. Casting fails when the meter can't cover the cost. zelda2/spell-costs

About: Zelda II: The Adventure of Link Magic meter

{
 "shield": [
  64,
  48,
  48,
  32,
  32,
  32,
  32,
  32
 ],
 "life": [
  140,
  140,
  120,
  120,
  100,
  100,
  100,
  100
 ],
 "thunder": [
  240,
  240,
  240,
  240,
  240,
  240,
  200,
  128
 ]
}

Cited by: Magic meter, Zelda II: The Adventure of Link

Zelda II's sword beam fires only when the life meter is exactly full, containers × 32 − 1; The Legend of Zelda fired it with up to half a heart missing. zelda2/full-life-beam

About: Zelda II: The Adventure of Link Sword beam

With the Fire spell on, the routine skips the beam check (Check_for_Fire_Spell, L3820-L3823).

Cited by: Sword beam, Zelda II: The Adventure of Link

Zelda II keeps The Legend of Zelda's locked-door rule. The Magic Key opens a door for free; otherwise a key is spent, and with no keys the door stays shut. zelda2/magic-key

About: Zelda II: The Adventure of Link Keys and locked doors

Cited by: Keys and locked doors, Zelda II: The Adventure of Link