Playthrough and payouts. The random number generator (RNG) is what turns slots into a game of chance; although players can use strategies to improve their experiplay for fun free slotsence, luck ultimately determines success. Also, every slot machine has a distinct set of rules that can impact gameplay & possible payouts, such as paylines, symbols, and bonus features. RTP Percentage (Return to Player). An additional crucial factor to take into account is the Return to Player (RTP) percentage concept.