I recall 3e having an attack of opportunity when a creature left the square within reach. So, if I could reach 10ft or 2 squares I would get an attack before the enemy got close enough to attack me at 5ft away. Now if I could reach 15ft (3squares) I used to have 2 attacks. I would think 5e simplified things with only 'reach' and not break it down more.
Heh. I remember "breakdancing" being part of the problem.Tumble.
Heh. I remember "breakdancing" being part of the problem.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.