The 8XY_ family is CHIP-8's arithmetic unit, and every member shares a layout selected by the last nibble. Today you open the family with 8XY0, which copies VY into VX, and wire up the sub-dispatch the rest of the ALU will hang off.
Dispatch the 8XY_ family by its low nibble and implement 8XY0 (set VX to VY).
The opcodes beginning with 8 are CHIP-8’s arithmetic and logic unit. They all read two registers, VX and VY, and the low nibble (n) selects which operation - 0 is copy, 1 through 3 are the logical ops, 4 and 5 and 7 are add and subtract, 6 and E are shifts. So the 0x8 arm of your main switch is really a second, nested switch on n. Setting that structure up now, on the simplest member, means each following lesson adds exactly one case.
8XY0 is that simplest member: “set VX to VY,” a plain register-to-register copy. It has no flag effect at all, which is worth pinning explicitly - the test holds VF at 0 across the copy and checks it stays there. That matters because the very next opcodes in this family do write VF, and it is easy to reach for a shared helper that touches the flag when it should not. Copy is the one that must leave VF completely alone.
case 0x8000:x, y := byte(op>>8&0x0F), byte(op>>4&0x0F)switch op & 0x000F { // the low nibble picks the ALU operationcase 0x0:v.V[x] = v.V[y]return nil}// an unmatched 8XY_ low nibble falls through to the// "unimplemented opcode" error, like every other unknown opcode