First impression lame "Defender" rip off, ends up not lame, badass when given the chance! Controls are unique and felt so weird at first. You can steer your ship only while firing, shields are always on when not firing, this layout gets to be so catchy I'd love to see real Defender adopt these controls. I never saw Repton during the 1980s.
The parallel to losing all men and going into hyperspace for Repton is when the enemy completes constructing their base station, the ground opens up around the base station and your ship gets sucked into the underground cavern, this action is called the "Failsafe Interlock Armageddon Bomb Activated". While down below, your shields, your nuke bombs, and your radar scanner thingy all malfunction to increase difficulty and you can crash into the cavern's floor and ceiling. You'll need these:
CHEAT MODE unlimited lives, VAPI disk image (works with and without SIO patch, loads faster with). 8 bytes
change offsets $68E0,68E1 from $C6 $AE to $EAEA
change offsets $68F3,68F4 from $C6 $AE to $EAEA
change offsets $C0E8,C0E9 from $C6 $AE to $EAEA
change offsets $C0FB,C0FC from $C6 $AE to $EAEA
CHEAT MODE unlimited nukes, edit 2 more bytes
change offsets $3E4D,3E4E from $C6 $AC to $EAEA
Repton's built in instructions are worth viewing. Cracked file versions broke the instructions, this disk has them.