This is a collection of my drawing by TikZ
\documentclass[tikz,border=2pt]{standalone}
\usepackage{ctex}
\usetikzlibrary{shadings}
\newcounter{density}
\setcounter{density}{20}
\begin{document}
\begin{tikzpicture}
\def\couleur{blue!10!green}
\path[coordinate] (0,0) coordinate(A)
++( 120:6cm) coordinate(B)
++(60:6cm) coordinate(C)
++(0:6cm) coordinate(D)
++(-60:6cm) coordinate(E)
++(240:6cm) coordinate(F)
;
\shade[shading=color wheel] (A) -- (B) -- (C) --(D) -- (E) -- (F)-- cycle;
\foreach \x in {1,...,60}{%
\pgfmathsetcounter{density}{\thedensity+10}
\setcounter{density}{\thedensity}
\path[coordinate] coordinate(X) at (A){};
\path[coordinate] (A) -- (B) coordinate[pos=.10](A)
-- (C) coordinate[pos=.10](B)
-- (D) coordinate[pos=.10](C)
-- (E) coordinate[pos=.10](D)
-- (F) coordinate[pos=.10](E)
-- (X) coordinate[pos=.10](F);
\draw[fill=\couleur!\thedensity] (A)--(B)--(C)-- (D) --(E) -- (F) -- cycle;
}
\end{tikzpicture}
\end{document} 
\documentclass[tikz,border=2pt]{standalone}
\usepackage{ctex,flowchart}
\begin{document}
\begin{tikzpicture}[>=stealth,font={\songti \small}]
\def\smbwd{2cm}
\node (terminal1) at (0,0) [draw, terminal,
minimum width=\smbwd,
minimum height=0.5cm] {START};
\node (predproc1) at (0,-1.5) [draw, predproc, align=left,
minimum width=\smbwd,
minimum height=1cm] {GET\\ DATA};
\node (decide1) at (0,-3.5) [draw, decision,
minimum width=\smbwd,
minimum height=1cm] {C$<$3};
\node (storage1) at (0,-5.5) [draw, storage,
minimum width=\smbwd,
minimum height=1cm] {STORE};
\node (process1) at (3,-5.5) [draw, process,
minimum width=\smbwd,
minimum height=1cm] {PROCESS};
\coordinate (point1) at (0,-6.75);
\node (terminal2) at (0,-7.75) [draw, terminal,
minimum width=\smbwd,
minimum height=0.5cm] {END};
\draw[->] (terminal1) -- (predproc1);
\draw[->] (predproc1) -- (decide1);
\draw[->] (decide1) -| node[above]{YES} (process1);
\draw[->] (decide1) -- (storage1);
\draw[->] (process1) |- (point1);
\draw[->] (storage1) -- (point1) -- (terminal2);
\end{tikzpicture}
\end{document} 
\documentclass[tikz,border=2pt]{standalone}
\usepackage{ctex}
\usetikzlibrary{mindmap}
\begin{document}
\begin{tikzpicture}
\path [
mindmap,
text = white,
level 1 concept/.append style =
{font=\Large\bfseries, sibling angle=90},
level 2 concept/.append style =
{font=\normalsize\bfseries},
level 3 concept/.append style =
{font=\small\bfseries},
tex/.style = {concept, ball color=white,
font=\Huge\bfseries},
分析/.style = {concept, ball color=green!50!black},
formats/.style = {concept, ball color=blue!50!black},
systems/.style = {concept, ball color=red!90!black},
editors/.style = {concept, ball color=orange!90!black}
]
node [tex,text=blue!80] {\scalebox{1.4}{IMC}} [clockwise from=0]
child[concept color=green!50!black, nodes={分析}] {
node {分析} [clockwise from=90]
child { node {数学分析} }
child { node {实分析} }
child { node {复分析} }
child { node {泛函分析} }
}
child [concept color=red, nodes={systems}] {
node {图论组合}}
child [concept color=blue, nodes={formats}] {
node {代数} [clockwise from=240]
child { node {线性代数} }
child { node {抽象代数} }
child { node {初等数论} }}
child [concept color=orange, nodes={editors}] {
node {概率论} };
\end{tikzpicture}
\end{document} 
\documentclass[tikz]{standalone}
\usepackage{ctex,amsmath,amssymb}
\everymath{\displaystyle}
\usetikzlibrary{mindmap,patterns}
\usepackage[hidelinks]{hyperref}
\begin{document}
\definecolor{tou}{RGB}{94,125,89}
\definecolor{author}{RGB}{225,244,225}
\definecolor{title}{RGB}{255,253,127}
\definecolor{left}{RGB}{148,176,107}
\definecolor{body}{RGB}{144,192,108}
\definecolor{body1}{RGB}{90,182,90}
\definecolor{topbot}{RGB}{60,92,76}
\newcommand{\yp}[1]{{\CJKfontspec{印品赤壁赋体}#1}}
\newcommand{\fz}[1]{{\CJKfontspec{方正黑体简体}#1}}
\newcommand{\ii}{\,\!\mathrm i\,\!}
\begin{tikzpicture}
\node[minimum width=17.7cm,minimum height=25cm,inner sep=0pt,outer sep=0pt,](box){};
\fill[body,top color=body1,bottom color=body](box.north west)--(box.north east)--(box.south east)--(box.south west)--cycle;
\draw[help lines,step=0.8cm,opacity=0.4](-8.85,-12.5)grid(8.85,12.5);
\node[align=center,text=author] at (box.center)
{\zihao{-2}\fz{向禹} \tikz{\draw(0.25,0.25)circle(0.25);\draw(0.25,0.25)circle(0.2);} \fz{译}
};
\fill[tou](-8.85,6.5)[bend left=25]to(8.85,10.8)--(box.north east)--(box.north west)--cycle;
\fill[left color=left,right color=tou](-8.85,6.5)[bend left=24]to(8.85,10.6)
--(8.85,9.6)[bend right=23]to(-8.85,6.5);
\node[text=title,align=center,scale=3]at(0,4){\fz{1994-2018年国际大学生}\\[-0.2cm]\fz{数学竞赛}};
\node[text=orange!20,align=center,scale=1.5]at(0,2){\fz{International Mathematics Competition}\\[-0.2cm]\fz{for University Students (1994-2018)}};
\node[opacity=0.5,draw,rounded corners] at(-2,7.8){$\int_a^bf(x)\,\mathrm dx=F(b)-F(a)$};
\node[opacity=0.5] at(5.4,7.8){\tikz{\draw[-stealth](-0.3,0)--(0,0)node[below left]{$O$}--(3.6,0)node[below=2pt]{$x$};
\draw[-stealth](0,-0.42)--(0,2)node[left]{$y$};
\draw(0,1.3)node[left]{$A$}..controls(1.4,0.6)and(2.2,2.4)..(2.8,1.7)node[right]{$B$}
--(2.8,0)node[below]{$C$};\node at(0.65,1.4){$f(x)$};}};
\node[opacity=0.6] at(-3.5,-3.5)
{
\scalebox{0.5}{\begin{tikzpicture}
\path [
mindmap,
text = white,
level 1 concept/.append style =
{font=\Large\bfseries, sibling angle=90},
level 2 concept/.append style =
{font=\normalsize\bfseries},
level 3 concept/.append style =
{font=\small\bfseries},
tex/.style = {concept, ball color=white,
font=\Huge\bfseries},
分析/.style = {concept, ball color=purple!90!black},
formats/.style = {concept, ball color=blue!50!black},
systems/.style = {concept, ball color=red!90!black},
editors/.style = {concept, ball color=orange!90!black}
]
node [tex,text=blue!80] {\scalebox{1.4}{IMC}} [clockwise from=0]
child[concept color=green!50!black, nodes={分析}] {
node {分析} [clockwise from=90]
child { node {数学分析} }
child { node {实分析} }
child { node {复分析} }
child { node {泛函分析} }
}
child [concept color=red, nodes={systems}] {
node {图论组合}}
child [concept color=blue, nodes={formats}] {
node {代数} [clockwise from=240]
child { node {线性代数} }
child { node {抽象代数} }
child { node {初等数论} }}
child [concept color=orange, nodes={editors}] {
node {概率论} };
\end{tikzpicture}}
};
\node[opacity=0.4]at(5.5,-2){
\begin{tikzpicture}[scale=10]
\begin{scope}
\clip (0,0) arc (-90:0:1/8) arc (90:180:1/8);
\fill[pattern=horizontal lines]
(0,0) arc (-90:0:1/8) --(1/16,1/16) arc (90:0:1/16);
\fill[pattern=vertical lines]
(0,0) arc (180:90:1/8) --(1/16,1/16) arc (0:90:1/16);
\end{scope}\node[below left](0,0){$O$};
\draw [-stealth](-1/8,0)--(0.34,0);\draw [-stealth](0,-1/8)--(0,0.34);
\node[below]at(0.34,0){$x$};\node[left]at(0,0.34){$y$};
\draw (0,0) arc (-90:90:1/8) (0,0) arc (-90:90:1/16)
(0,0) arc (180:0:1/8) (0,0) arc (180:0:1/16) (0,0)--(1/8,1/8);
\fill[fill=body](0.085,0.085)node[inner sep=0pt]{$D$}circle(0.01);
\draw(0,1/8)circle(1/8);\draw(0,1/16)circle(1/16);
\draw(1/8,0)circle(1/8);\draw(1/16,0)circle(1/16);
\node[above left]at(0,1/4){$\tfrac12$};\node[above left]at(0,1/8){$\tfrac14$};
\end{tikzpicture}
};
\node[opacity=0.3] at(3,-6.5){$\left( \sum_{n=1}^{\infty}{a_{n}^{2}} \right) \left( \sum_{n=1}^{\infty}{b_{n}^{2}} \right) \geqslant \left( \sum_{n=1}^{\infty}{a_nb_n} \right) ^2$};
\node[opacity=0.3] at(0,-8){$f(z)=\frac1{2\pi\ii}\oint_C\frac{f(\xi)}{\xi-z}\,\mathrm d\xi$};
\fill[tou](-8.85,-10.5)--(-8.85,-12.5)--(8.85,-12.5)--(8.85,-10.5)--cycle;
\node[anchor=north,align=left,text=author]at(0,-10.7){
\begin{tikzpicture}[color=author]
\draw[very thick,rounded corners](0,0)--(0,1.3)--(1.3,1.3)--(1.3,0)--cycle;
\fill(0.65,1.08)circle(0.12);
\fill(0.15,0.93)--(0.65,0.8)--(1.15,0.93)--(1.15,0.98)--(0.65,0.85)--(0.15,0.98)--cycle;
\foreach \x in{-0.12cm,-0.16cm,-0.2cm}
\fill[yshift=\x](0.15,0.93)--(0.65,0.8)--(1.15,0.93)--(1.15,0.98)--(0.65,0.85)
--(0.15,0.98)--cycle;
\foreach \x in{-0.32cm,-0.36cm,-0.4cm,-0.44cm,-0.48cm,-0.52cm,-0.56cm,-0.6cm,-0.64cm}
\fill[yshift=\x](0.15,0.93)--(0.65,0.8)--(1.15,0.93)--(1.15,0.98)--(0.65,0.85)
--(0.15,0.98)--cycle;
\end{tikzpicture}
\parbox{4cm}{\vspace{-1.2cm}
\scalebox{1.7}{\yp{无名出版社}}\\[-2mm]
\scalebox{0.5}[1]{PUBLISHING HOUSE OF NONAME}\\[-2mm]
\href{yuxtech.github.io}{yuxtech.github.io}
}};
\end{tikzpicture}
\end{document} 
\documentclass[tikz]{standalone}
\usetikzlibrary{automata,positioning,shadows}
\begin{document}
\begin{tikzpicture}[shorten >=1pt,node distance=2cm,on grid,>=stealth,thick,
every state/.style={fill,draw=none,orange,text=white,circular drop shadow},
accepting/.style={green!50!black,text=white},
initial/.style={red,text=white}
]
\node[state,initial](q_0) {$q_0$};
\node[state] (q_1)[above right=of q_0] {$q_1$};
\node[state] (q_2)[below right=of q_0] {$q_2$};
\node[state,accepting] (q_3)[above right=of q_2] {$q_3$};
\path[->](q_0)edge node[above left] {$0$}(q_1)
edge node[below left] {$1$}(q_2)
(q_1)edge node[above right]{$1$}(q_3)
edge[loop above]node {$0$}()
(q_2)edge node[below right]{$0$}(q_3)
edge[loop below]node {$1$}();
\end{tikzpicture}
\end{document} 
\documentclass[tikz]{standalone}
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}[scale=0.4,auto,decision/.style={diamond,draw=blue,thick,fill=blue!20,
text width=4.5em,align=flush center,inner sep=1pt},
block/.style={rectangle,draw=blue,thick,fill=blue!20,
text width=5em,align=center,rounded corners,minimum height=4em},
line/.style={draw,thick,-stealth,shorten >=2pt},
cloud/.style={draw=red,thick,ellipse,fill=red!20,minimum height=2em}]
\matrix[column sep=4mm,row sep=7mm]
{\node[cloud](expert){expert};&
\node[block](init){initialize model};&
\node[cloud](system){system};\\
&\node[block](identify){identify candidate model};&\\
\node[block](update){update model};&
\node[block](evaluate){evaluate candidate models};&\\
&\node[decision](decide){is best candidate};&\\
&\node[block](stop){stop};&\\
};
\begin{scope}[every path/.style=line]
\path (init)--(identify);
\path (identify)--(evaluate);
\path (evaluate)--(decide);
\path (update)|-(identify);
\path (decide)-|node[near start]{yes}(update);
\path (decide)--(stop);
\path[dashed] (expert)--(init);
\path[dashed] (system)--(init);
\path[dashed] (system)|-(evaluate);
\end{scope}
\end{tikzpicture}
\end{document} 
\documentclass[tikz,svgnames]{standalone}
\usepackage{pgfornament,amsmath}
\usetikzlibrary{shapes.symbols}
\begin{document}
\begin{tikzpicture}
\begin{scope}[color=Maroon]
\draw[help lines](-7,-7)grid(7,7);
\node[minimum size=14cm](current page1){};
\node[anchor=north west] at (current page1.north west)
{\pgfornament[width=5cm]{35}};
\node[anchor=north east] at (current page1.north east)
{\pgfornament[width=5cm]{36}};
\node[anchor=south west] at (current page1.south west)
{\pgfornament[width=5cm,symmetry=h]{35}};
\node[anchor=south east] at (current page1.south east)
{\pgfornament[width=5cm,symmetry=h]{36}};
\node[scale=2.5,green!45!black,cloud,cloud puffs=14,draw=red]at(current page1.center){\parbox{4cm}{$\displaystyle\int_{-\infty}^{+\infty}{\text{e}^{-x^2}\sin \left( \frac{\pi }{2x^2} \right) \text{d}x}$\\$=\sqrt{\pi}\text{e}^{-\sqrt{\pi}}\sin \left( \sqrt{\pi} \right)$}};
\end{scope}
\end{tikzpicture}
\end{document}