Vertical space before horizontal line

Question

I have defined an exercise environment which ends with a horizontal rule. I want to have some vertical space between the end of the environment text and the rule. When I try to insert that, the vertical space ends up after (below) the rule instead of before it.

I have tried both \medskip at the beginning of the HorzLine command, and \vspace{5\bigskipamount} before the \HorzLine at the exercise environment, and both don't work.

What's going on?

Here is some code:

\documentclass[a4paper,10pt]{article}
\usepackage[english]{babel}
\usepackage{blindtext}
\usepackage{color}

\definecolor{orange}{rgb}{1,.549,0}

\newcommand{\HorzLine}{\medskip\noindent\textcolor{orange}{\rule{\textwidth}{5pt}}}

\newenvironment{exercise}
{\noindent\small\textbf{Exercise:}}
{\vspace{5\bigskipamount}\HorzLine}

\begin{document}
    \begin{exercise}
        \blindtext
    \end{exercise}
    \blindtext
\end{document}

Answer 1

\vspace doesn't take effect until you are in vertical mode. \blindtext probably doesn't end with \par or a blank line, so it's still in horizontal mode when the environment ends. put \par at the beginning of the end code for the environment to force the vertical space above the rule:

{\par\nobreak\vspace{5\bigskipamount}\HorzLine}

EDIT: added \nobreak to prevent a page break just before the \HorzLine.

Answer 2

Simply change \vspace{5\bigskipamount} to \vskip5\bigskipamount solve the problem

Answer 3

You need to leave some whitespace in your code between the \vspace and the \HorzLine:

\newenvironment{exercise}
{\noindent\small\textbf{Exercise:}}
{\vspace{5\bigskipamount}

\HorzLine}

The whitespace changes the mode TeX is in.