UFO games the US publisher of Raiden IV, rather surreptitiously has provided a “Raiden IV Secret File”  downloadable PDF document.  Contained inside is some great looking high-resolution art, technical blow-out drawings of nearly every enemy in the game, damage tables for the various weapons and sub-weapons in the game and most notably, locations for almost all the hidden ‘Sol’ towers in each level.

Click here to download it for yourself.