For those asking about how randomizer logic works to ensure that the game is still playable, you can have a look at the Super Metroid randomizer logic.
https://github.com/tewtal/itemrandomizerweb
The randomizer logic, depending on difficulty level selected, will ensure that certain items are available and the game is still playable. There are lots of different checks like this to compensate for various techniques, sequences, etc.
One common technique in Super Metroid is called "hell running", which means getting through the heated rooms of Upper Norfair without Varia Suit, an item that provides protection against heat. In "Casual" mode, the randomizer requires that you are given this protection before making you go to these areas. In "Hard" mode, the randomizer requires you have either 3 Energy Tanks or Varia Suit.