Alignment and width with tcolorbox

Question

I'm writing a document where I need to put some text inside a box. I have figured out how to make a rounded-corner box with the graphical appearence I was looking for.

My code is the following:

\documentclass[11pt, a4paper]{report} 
\usepackage[utf8]{inputenc} 
\usepackage[most]{tcolorbox}

\definecolor{mycolor}{rgb}{0.122, 0.435, 0.698}

\newtcbox{\mybox}{enhanced,
  colframe=mycolor,colback=mycolor!7!white,
  boxrule=0.5pt,arc=4pt,boxsep=0pt,left=6pt,right=6pt,top=5pt,bottom=5pt, hbox}


\begin{document}

\mybox{\textbf{Assumption 1:} Atmospheric forces can be neglected.}

\end{document}

With the following output:

I would like to know how:

1. Indent the box when it is located at the beginning of a section or paragraph. I've tried \indent but it seems to not work.

2. How to control the width of the box. When I write a long text it exceeds the page margins. I would like to set the width to constrain the box size and force the text to fit inside the width I have choosen (just in case of a long text).

3. When a long text wraps to start a new line within the box, I would like to get an alignment just after the colon, i.e. ":", and not with the first world of the box as normally happens.

4. It is more a curiosity: I've defined a \tcbset{enhanced,colframe={violet!60},colback={black!3!white}, drop shadow} for another box inside the document. Why my "assumption box" acquires the drop shadow option and displays it?

Here some examples of the result I would like to get:

I would appreciate a lot any kind of help. However, It would be great If someone could provide me a MWE to accomplish the whole task. Thank you very much.

Answer 1

tcolorbox offers two kind of boxes tcbox and tcolorbox. First ones are for a short texts which won't break in lines while seconds can contain longer texts and use a whole line as default width. Therefore, I think that what OP wants is not possible with a unique command.

Following code proposes an environment (tcolorbox) for the larger boxes. The inner contents described by OP looks like a description environment. I've assumed that the box only contains one item. The alignment has been taken from an egreg`s answer

longbox environment has one optional and one mandatory parameters. The mandatory is the item title while the optional will be applied as tcolorbox options to change box format (even width).

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[shortlabels]{enumitem}
\usepackage{lipsum}
\usepackage{lmodern}
\usepackage[most]{tcolorbox}

\definecolor{mycolor}{rgb}{0.122, 0.435, 0.698}

\newlength{\xdescwd}
\newenvironment{xdesc}[1]
  {\settowidth{\xdescwd}{\textbf{#1:}}%
   \begin{description}[leftmargin=\dimexpr\xdescwd+.5em\relax,
     labelindent=0pt,labelsep=.5em,
     labelwidth=\xdescwd,align=right]\item[#1:]}
  {\end{description}}

\newtcolorbox{longbox}[2][]{before upper={\begin{xdesc}{#2}},after upper={\end{xdesc}}, 
    enhanced, breakable, colframe=mycolor,colback=mycolor!7!white,
    boxrule=0.5pt, arc=4pt, boxsep=0pt, left=6pt, right=6pt, top=5pt, bottom=5pt, #1}

\begin{document}

\lipsum[1]

\begin{longbox}[width=.8\linewidth]{Assumption 1}
\lipsum[2][1-3]
\end{longbox}

\begin{longbox}[colback=red!30, sharp corners]{Example}
\lipsum[2][1-3]
\end{longbox}

\begin{longbox}{Example}
Only one line
\end{longbox}
\end{document}