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Help your crab beat up all the other crabs at the beach by programming assembly. Don’t forget you only move sideways. Read the manual below to proceed.

Play Now

I made this game for a local 6 hour game jam. It is unpolished but very fun to play!

Theme music:

Crab VM

There are 5 registers AMVHR:

  • A: General purpose accumulator. Default argument for some op codes as documented below.

  • M: Motor control. Your crab can only crawl sideways. M controls its movement. If it’s positive, then it moves to the right and vice versa. Note: movement is only actuated for every cycle after M register has been set.

MOV 1 M     ; no movement
NOP         ; moves 1 to the right
NOP         ; moves 1 to the right
MOV 0 M     ; moves 1 to the right
NOP         ; stands still
MOV -10 M   ; stands still
NOP         ; moves 1 to the left

  • V, H: General purpose register. Originally intended for object detection

  • R: Rotation mod 4. Note: 0 is down, increments clockwise. This register is readonly but can be indirectly changed via RCC and RCW instructions.

Instructions

  • LABEL:: Labels must be on their own line (cannot be followed by other instructions unlike zachtronics games).
MOV 10 A
L:
SUB 1 A
JGZ L
  • MOV
MOV 1 A
MOV R A
  • ADD, SUB
ADD 1 A
ADD A A
SUB 1 M
  • NEG reg: Negates value in register.
NEG M

  • NOP No operation. Also known as noop

  • JMP label: Point the instruction pointer to specified label.

  • JEZ: Jump if A == 0

  • JNZ: Jump if A != 0

  • JGZ: Jump if A > 0

  • JLZ: Jump if A < 0

  • JRO: Unconditional relative jump with immediate value or value from register.

JRO -1      ; jump to previous instruction
JRO 1       ; jump to following instruction
JRO A       ; relative to jump the instruction stored in A

  • RCW: Rotate clockwise

  • RCC: Rotate counterclockwise

Example program:

The first level can be solved using this code:

MOV -1 M
L:
JMP L

User interface

Use C-return to step through your code.

Press Esc or C-c to stop debugger.

Future improvements

The game is surprisingly fun and in the future I would like to add mechanics such as boss fights, object detection, fork/join (similar to REPL in Exapunks).

Link to source code