18-magicnumber.md

build bytecode by hand using https://ethervm.io/

store 42 at memory 0x0 then return memory 0x0:

• PUSH 0x2A (42)
• PUSH 0x00 (memory location 0)
• MSTORE
• PUSH 0x20 (length)
• PUSH 0x00 (memory location 0)
• RETURN

602A 6000 52 6020 6000 F3

deploy code 1:

• PUSH 0x0A (length of runtime code, 10 bytes)
• PUSH 0x0C (offset to runtime code, deploy code is 12 bytes so offset is 13)
• PUSH 0x00 (destination offset)
• CODECOPY
• PUSH 0x0A (length of code, 10 bytes)
• PUSH 0x00 (offset is 0)
• RETURN

600A 600C 6000 39 600A 6000 F3

And send the transaction to create the contract:

sendTransaction({
  from: player,
  to: null,
  data: '600A600C600039600A6000F3602A60005260206000F3'
});