And Sony vs Bleem (or the IBM BIOS reimplementation) already set a precedent so that doesn't really matter anymore. Look at Wine. Or Exegutor. Or DOSBox.

All of them totally legal reimplementing either prior look and feel and functionality.

> The code of computer programs are excluded from design protection, but visual aspects of software are very commonly protectable as long as they are ‘new’ (i.e. not a direct copy of anything that has come before) and possess ‘individual character’ (i.e. that the design produces a different ‘overall impression’ than anything that has come before)

I'm no expect, but Chris Sawyer style games certainly provided a unique overall impression to me. Whether it needs to be a registered design or not I couldn't say, but it's not going to be cheap to find out.

More recent battles have relied on Trademark and Patent law rather than Copyright, but "Look and Feel" is still a legal grey area