export declare class zimu {
    private currentLetter;
    private step;
    private isForward;
    private history;
    constructor(startLetter?: string);
    setStep(step: number): void;
    setDirection(isForward: boolean): void;
    getNextLetter(): string;
    generateSequence(length: number): string[];
    getHistory(): string[];
    reset(startLetter?: string): void;
}