Mechanic · movement · metroidvania, platformer

Morph ball

A form in which the character curls into a small ball that rolls along the ground.

stubAlso: Maru Mari, Morphing Ball, morphballUpdated 2026-10-21
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  2. Games
  3. References
  4. Sources

The morph ball shrinks the character into a ball that rolls. In Metroid Samus rolls into it only on the ground and only with the Maru Mari, and a jump press unrolls her1. Metroid II gives her the ball with no item2, and its Spring Ball lets the ball jump3. Super Metroid makes the ball an item again, and its top speed on the ground, 3.25 px/frame, is above running’s 2.754.

  • Super Metroid (1994). An item, with a top speed on the ground above running's.4
  • No jumpMetroid (1986). The Maru Mari, from the ground only; a jump press unrolls it.1
  • Spring upgradeMetroid II: Return of Samus (1991). Available from the start; the Spring Ball lets it jump.2,3

See also

Games

GameYearHowNote
Super Metroid1994an item, with a top speed on the ground above running's
Metroid1986No jumpthe Maru Mari, from the ground only; a jump press unrolls it
Metroid II: Return of Samus1991Spring upgradeavailable from the start; the Spring Ball lets it jump
Every claim about this mechanic, by game (4)
Metroid 1986Samus rolls into the ball only with the Maru Mari (gr_MARUMARI) and only on the ground. In the ball, Up or a jump press unrolls her unless Down is held, and only if she has room to stand.Code
Metroid II: Return of Samus 1991The morph ball needs no item: a Down press while crouching calls samus_morphOnGround, and the item bits list bombs, Hi-Jump, Screw Attack, Space Jump, Spring Ball, Spider Ball, and Varia, with no bit for the ball. A new game starts with no item bits set.Code
In the morph ball, A starts a jump only with the Spring Ball, from a counter of $2E.Code
Super Metroid 1994The morphing transition reverts Samus's pose unless the Morph Ball is equipped. On the ground the ball's row of the speed table tops out at 3.25 px/frame, above running's 2.75.Code

References

  1. ^ abSamus rolls into the ball only with the Maru Mari (gr_MARUMARI) and only on the ground. In the ball, Up or a jump press unrolls her unless Down is held, and only if she has room to stand.Codenmikstas/metroid-disassembly
    How we know
    2794SetSamusRoll:
2795LD0B5:  lda SamusGear
2796    and #gr_MARUMARI
2797    beq +      ; branch if Samus doesn't have Maru Mari
2798    lda SamusGravity
2799    bne +
    Source_Files/Bank07.asm lines 2794–2799 at 4270d57 · upstream ↗
    2820    SamusRoll:
2821    lda Joy1Change
2822    and #$08     ; UP pressed?
2823    bne +      ; branch if yes
2824    bit Joy1Change  ; JUMP pressed?
2825    bpl ++    ; branch if no
2826*   lda Joy1Status
2827    and #$04       ; DOWN pressed?
2828    bne +     ; branch if yes
2829;break out of "ball mode"
⋮
2834    jsr CheckMoveUp
    Source_Files/Bank07.asm lines 2820–2834 at 4270d57 · upstream ↗

    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. ^ abThe morph ball needs no item: a Down press while crouching calls samus_morphOnGround, and the item bits list bombs, Hi-Jump, Screw Attack, Space Jump, Spring Ball, Spider Ball, and Varia, with no bit for the ball. A new game starts with no item bits set.Codealex-west/M2RoS
    How we know
    3705; Handle down input
3706    ; Rising edge
3707    ldh a, [hInputRisingEdge]
3708    bit PADB_DOWN, a
3709    jr z, .endIf_L
3710        call samus_morphOnGround
    SRC/bank_000.asm lines 3705–3710 at 031aea3 · upstream ↗
    4524samus_morphOnGround: ;{ 00:1BA4
4525    ; Set pose
4526    ld a, pose_morph
4527    ld [samusPose], a
    SRC/bank_000.asm lines 4524–4527 at 031aea3 · upstream ↗
    49def itemMask_bomb   = %00000001 ; 01: Bombs
⋮
53def itemMask_spring = %00010000 ; 10: Spring ball
54def itemMask_spider = %00100000 ; 20: Spider ball
55def itemMask_varia  = %01000000 ; 40: Varia suit
56def itemMask_UNUSED = %10000000 ; 80: Unused
    SRC/constants.asm lines 49–56 at 031aea3 · upstream ↗
    20    db $00       ; Samus' equipment
    SRC/data/initialSave.asm line 20 at 031aea3 · upstream ↗

    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. ^ abIn the morph ball, A starts a jump only with the Spring Ball, from a counter of $2E.Codealex-west/M2RoS
    How we know
    3780    ; Handle spring ball
3781    ; Check if A is pressed
3782    ldh a, [hInputPressed]
3783    bit PADB_A, a
3784    jr z, .endIf_C
3785        ; Check if we have spring ball
3786        ld a, [samusItems]
3787        bit itemBit_spring, a
3788        jr z, .endIf_C
3789            ; Set jump parameter
3790            ld a, samus_jumpArrayBaseOffset - $12 ;$2e
    SRC/bank_000.asm lines 3780–3793 at 031aea3 · upstream ↗

    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

  4. ^ abThe morphing transition reverts Samus's pose unless the Morph Ball is equipped. On the ground the ball's row of the speed table tops out at 3.25 px/frame, above running's 2.75.CodeInsaneFirebat/sm_disassembly
    How we know
    15801InitializeSamusPose_MorphingTransition:
⋮
15819  .noMorphBall:
    src/bank_91.asm lines 15801–15822 at 7af131e · upstream ↗
    5200    dd wordSwap($0030*!SPF*$100),wordSwap($02C0*!SPF*$100),           wordSwap($0080*!SPF*$100) ; 1: Running
⋮
5203    dd wordSwap($00C0*!SPF*$100),wordSwap($0340*!SPF*$100),           wordSwap($0080*!SPF*$100) ; 4: Morph ball - on ground
    src/bank_90.asm lines 5200–5203 at 7af131e · upstream ↗

    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

Sources

Code