Physics can be quirky, and quick reactions are needed. i find the drag-and-drop mechanic essential for matching candies quickly and avoiding chaos in CANDY KILLER.
Click and drag candies, matching them before they fall off, which is kinda weird anyway, you need fast reflexes to succeed. Make combos and react quickly as candies stack, and you will improve.
Inside the game, the buttons are simple to use, just click and drag candies to match them, which is kinda weird anyway, and their physics can be wonky sometimes. i think it's designed to make quick moves important.
Quick matches are best, and then look for combo opportunities first, i discovered that matching many candies in one move keeps your score high, even if it’s frustrating sometimes.
Things like controls, physics, and matching mechanics are the essentials, and this game stuff is simple, lightweight, with addictive features that make you keep playing longer than you planned.