As a distant relative of ol' Frank you have discovered the location of the monster, reduced your size and that of a passing submarine, to one sufficiently small to allow you to journey in through the mouth and on round his body triggering the start of a new life.
Starting in the trachea, you must steer your sub round hordes of green frogs. Get it? Frogs in the throat! If you don't suffer too much damage, or use up all your oxygen, you can then start on the right lung, avoiding marauding ciggie packets, the left lung where CO2 canisters and clouds lurk, and on to the stomach, collecting spanners with which to effect repairs en-route.
In the tummy, avoid the fried eggs, but collect the greasy bacon for use as a lubricant. I couldn't get any further; ran out of air! But I'm reliably informed that the heart and brain are similarly tricky. Every now and then, you get the chance to zap rampant oxygen molecules thus replenishing your supply.
The graphics are excellent bearing a striking similarity to the real thing. In fact, the whole production is very well done, down to the loading screen, sound, movement and controls. It's a really silly idea, but the humour of the concept and the slick presentation are very appealing.
Just one gripe. This appears to be a conversion from an Electron game. Why can't I zap the dreaded throat frogs or fag packets or fried eggs in this version?