simplest

elemental fundamental rudimentary straightforward underlying

ABCs abecedarian basal beginning child's play clear duck soup easy essential facile foundational initial introductory meat and potatoes original plain prefatory preliminary primary primitive primo simplex simplified substratal uncomplex uncomplicated

additional advanced extra secondary

abstruse complex complicated compound difficult hard intricate involved

ABCs abecedarian basal basic beginning child's play clear duck soup easy elemental essential facile foundational fundamental initial introductory meat and potatoes original plain prefatory preliminary primary primitive primo rudimentary simplex simplified straightforward substratal uncomplex uncomplicated underlying

elemental elementary embryonic primitive simple

abecedarian basal beginning early immature initial introductory larval nuts-and-bolts primary uncompleted undeveloped vestigial

complex complicated difficult intricate sophisticated

additional advanced derivative developed extra nonessential