Leviathan by English Software is a good Zaxxon clone,
in the snapshots the Leviathan Amiga Version.
English Software was set up in 1982 by Philip Morris. By the end of 1983, English Software was the largest producer of Atari 8-bit software in the UK and Morris closed Gemini Electronics to concentrate on English.
Popular games include Jet-Boot Jack (1983) and Henry’s House (1984), racer Elektra Glide (1985), the multi-event Knight Games (1986) and shoot ’em up Leviathan (1987).
English had licensing deals that saw some of their games released internationally e.g. through Dynamics Marketing in Germany and Datamost in the US. A number of English’s games were sold at budget price by Mastertronic in the US, which included exclusive ports such as the Atari version of Henry’s House and the PC version of Knight Games. Philip Morris said in 2013 he did not license the Atari version to Mastertronic UK, even though English Software had the option to do this. How they managed to publish it is a mystery.