Ys I: Ancient Ys Vanished

The player controls Adol on a game field viewed from a top-down perspective. As he travels on the main field and explores dungeons, he will encounter numerous roaming enemies, which he must battle in order to progress.

Combat in Ys is rather different from other RPGs at the time, which either had turn-based battles or a manually activated sword. Ys instead features a battle system where Adol automatically attacks when walking into enemies off-center. When the protagonist moves toward his enemy, damage is sustained on both sides. Attacking straight on causes the attacker the most damage to himself, but clipping the edge of the defender yields a successful differential. This combat system was created with accessibility in mind. This 'bump attack' system has become one of the series' defining features. Falcom staff have compared this style of gameplay to the enjoyment of popping air bubble sheets, in the sense that it took the tedious task of level-grinding and turned it into something similar to a high-score-based arcade game. According to GamesTM and John Szczepaniak (of Retro Gamer and The Escapist), "Repetition of the act was pleasurable as you developed a psychological rhythm and, even in the event of backtracking, progress was always swift since the player never needed to stop moving."

Another feature that has been used in nearly every Ys title since the original is the recharging health mechanic, which had previously only been used in the Hydlide series. Recharging health has since become a common mechanic used in many video games today.