Boulder Dash co-creator Peter Liepa created Boulder Dash II on Atari 8-bit machines first, before converting it to the Commodore 64. He’s said openly in interviews that he prefers Atari‘s machine when it comes to programming games, so it should come as no surprise to find arguably the best version of Boulder Dash II on the Atari 8-bit.
As far as I know, though, it was only released in North America as part of the “Super Boulder Dash” package from Electronic Arts (alongside a re-release of the first Boulder Dash). The Atari 8-bit version was never released as a stand-alone game. At least not by First Star Software.
Everything about the game is perfectly realised: the control system, the graphics, the scrolling, the music and sound effects.
This sequel features sixteen new caves, all designed by the original author, and they are a mix of difficulties. Some are hair-tearingly hard, while others are quite easy when you figure out what the key to solving them is.
In my opinion Boulder Dash II runs a close second to the classic Boulder Dash, and is way ahead of anything that came afterwards, and I include any of the many homebrew versions of the game in that equation.
Boulder Dash II was first published in 1985 by First Star Software.
See also: Boulder Dash Special