ChangeController.cs

/// <summary>
/// Move the ChangeController's current index forward by index.
/// Positive values only, wil only result in forward movement (if any).
/// </summary>
/// <param name="n">The number of times to move forward.</param>
public void Forward(int n = 1) {
    if (n < 0)
        throw new ArgumentOutOfRangeException(nameof(n));

    for (int i = 0; i < n; i++) {
        Change cur = _changes[++Index];
        Current[cur.X, cur.Y] = cur.New;
        SetDirty(new Vector2Int(cur.X, cur.Y));
    }
}