The goal of 'gsDesign2' is to enable fixed or group sequential
    design under non-proportional hazards. To enable highly flexible enrollment,
    time-to-event and time-to-dropout assumptions, 'gsDesign2' offers piecewise
    constant enrollment, failure rates, and dropout rates for a stratified
    population. This package includes three methods for designs:
    average hazard ratio, weighted logrank tests in Yung and Liu (2019)
    <doi:10.1111/biom.13196>, and MaxCombo tests.
    Substantial flexibility on top of what is in the 'gsDesign' package
    is intended for selecting boundaries.

Provides tools for planning and simulating recurrent event trials
    with overdispersed count endpoints analyzed using negative binomial (or
    Poisson) rate models. Implements sample size and power calculations for
    fixed designs with variable accrual, dropout, maximum follow-up, and event
    gaps, including methods of Zhu and Lakkis (2014) <doi:10.1002/sim.5947> and
    Friede and Schmidli (2010) <doi:10.3414/ME09-02-0060> as well as
    extensions for score-test sizing and gaps between events. Supports group
    sequential monitoring by building on the 'gsDesign' package.
    Includes recurrent-event simulation utilities (including seasonal rates),
    interim data truncation, Wald and score-test inference for rate ratios,
    and information estimation and sample size re-estimation with or without
    treatment-group labels.

Provides systematic, dependency-aware exploration of
    group sequential designs created with 'gsDesign'.
    Supports reproducible grid and random search over user-defined
    candidate sets, parallel evaluation via the 'future' framework,
    standardized metric extraction, and auditable reporting for
    design-space evaluation and trade-off analysis.
    Methods for group sequential design are described in
    Anderson (2025) <doi:10.32614/CRAN.package.gsDesign>.
    The 'future' framework for parallel processing is described in
    Bengtsson (2021) <doi:10.32614/RJ-2021-048>.