Microlite ’81 is now available in a tablet-friendly edition. The author writes;
The Microlite81 rules are based on the two boxed sets (Basic and Expert) published in 1981, often referred to as B/X. The rules are not intended to be a clone of the B/X rules, but rather a conversion of them to a rules-lite D20-based system that encourages old-school play without strictly old-school rules. Microlite81 is based on the third edition of the original Microlite74 rules.