Screw Attack

References

1. ^ abIsScrewAttackActive counts the Screw Attack as on only in the running state with the item: in a somersault, or in the plain jump animation while Samus still rises. The Samus-enemy crash code at LF282 calls it.Codenmikstas/metroid-disassembly
   How we know

   2362IsScrewAttackActive:
   2363LCD9C:  SEC             ;Assume screw attack is not active.
   2364LCD9D:  LDY ObjAction           ;
   2365LCDA0:  DEY             ;Is Samus running?
   2366LCDA1:  BNE ++              ;If not, branch to exit.
   2367LCDA3:  LDA SamusGear           ;
   2368LCDA6:  AND #gr_SCREWATTACK     ;Does Samus have screw attack?
   2369LCDA8:  BEQ ++              ;If not, branch to exit.
   2370LCDAA:  LDA AnimResetIndex      ;
   2371LCDAD:  CMP #an_SamusSalto      ;Is Samus summersaulting?
   2372LCDAF:  BEQ +               ;If so, branch to clear carry(screw attack active).
   2373LCDB1:  CMP #an_SamusJump       ;
   ⋮
   

   7935LF282:  bcs Exit17
   7936    jsr LF2E8
   7937    jsr IsScrewAttackActive     ;($CD9C)Check if screw attack active.
   

   865.alias sa_Run           1   ;Also run and jump.
   866.alias sa_Jump          2
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

2. ^ abWith the Screw Attack, an enemy Samus touches in a spin jump or its start pose takes a Screw Attack weapon hit, and the contact doesn't hurt her. Solid enemies, whose damage entry is $FF, are exempt.Codealex-west/M2RoS
   How we know

   8850    ; Check if screw attack is active
   8851    ld a, [samusItems]
   8852    bit itemBit_screw, a
   8853        jr z, .iceCase
   8854    ld a, [samusPose]
   8855    cp pose_spinJump
   8856        jr z, .screwCase
   8857    ld a, [samusPose]
   8858    cp pose_spinStart
   ⋮
   8878    ; Don't screw if damage is $FF (enemy is solid)
   ⋮
   8885    ; Hurt flag is not set here, so Samus will not be damaged by this
   ⋮
   8890    ; Save weapon type to Screw Attack
   ⋮
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

3. ^ abA normal enemy's touch routine takes another path when ContactDamageIndex is nonzero: it damages the enemy and returns without hurting Samus. Its comment places the Screw Attack's damage at $A4C2, 2000 ($07D0) for index 3, before the enemy's vulnerability scales it.CodeInsaneFirebat/sm_disassembly
   How we know

   4812NormalEnemyTouchAI_NoDeathCheck:
   4813; Damage values:
   4814;     Speed boosting:      $A4AF
   4815;     Shinesparking:       $A4BA
   4816;     Screw attack:        $A4C2
   4817;     Pseudo screw attack: $A4CC
   

   LDA.L EnemyVulnerabilities_power,X … LDA.W Enemy.health,X SEC SBC.B DP_Temp12

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger