mjhjmtu

I was trying to reproduce the following picture:

I've got the following MWE:

documentclass[border=5pt,tikz]standalone
definecolorhellblauRGB18,158,181
definecolordunkelblauRGB22,141,163
pagecolorhellblau
newcommandchangefont[3]fontfamily#1fontseries#2fontshape#3selectfont
tikzstylekreis = [fill=white,inner sep=3pt,circle]
begindocument
 begintikzpicture
 clip (-3,-1.5) rectangle (4,2);
 fill[dunkelblau] (210:1.65) -- (210:1) -- (150:1) -- (90:1) -- (30:1) -- (30:2) --+ (-30:1) -- ([xshift=1.71cm]30:2.15) -- (5,0) -- (5,-1.5) --+ (-5.5,0) -- cycle;
 fill[dunkelblau,yshift=-.13cm] (151:1.59) --+ (.56,-.5) -- ([yshift=.15cm]150:1) -- ([yshift=.15cm]150:1.5) -- cycle;
 draw[rotate=30,ultra thick,white] (0:1) -- (60:1) -- (2*60:1) -- (3*60:1) -- (4*60:1) -- (5*60:1) -- (6*60:1) -- cycle;
 draw[ultra thick,white] (150:1) -- (150:1.5) node[kreis] ;
 draw[ultra thick,white] (210:1) -- (210:1.5) node[kreis] ;
 draw[ultra thick,white] (30:1) -- (30:2) --+ (-30:1);
 draw[xshift=1.71cm,very thick,white] (30:1) -- (30:2) node[kreis] ;
 node[white,below] at (-2,2) changefontpagbnDopamine;
 endtikzpicture
enddocument

And here is the output:

My question is: How can I draw the shadow in the background (with the color dunkelblau!80) in a more effective way?

Note sure if it is more efficient, but it is a lot easier to work with if you define the coordinates first, and then draw them.

BTW: +1 for a nice usable MWE

documentclass[border=5pt,tikz]standalone

usetikzlibrarybackgrounds,calc

definecolorhellblauRGB18,158,181
definecolordunkelblauRGB22,141,163
newcommandchangefont[3]fontfamily#1fontseries#2fontshape#3selectfont
tikzstylekreis = [fill=white,inner sep=3pt,circle]
begindocument
begintikzpicture[
 % https://tex.stackexchange.com/a/230228/3929
 background rectangle/.style=fill=hellblau!60, show background rectangle
 ]
 coordinate (C1) at (-3,-1.5);
 coordinate (C2) at (4,2);

 clip (C1) rectangle (C2);

 % hexagon points
 coordinate (M1) at (0+30:1);
 coordinate (M2) at (60+30:1);
 coordinate (M3) at (2*60+30:1);
 coordinate (M4) at (3*60+30:1);
 coordinate (M5) at (4*60+30:1);
 coordinate (M6) at (5*60+30:1);
 coordinate (M7) at (6*60+30:1); % = M1

 % points for white circles
 coordinate (N1) at (150:1.5);
 coordinate (N2) at (210:1.5);

 % away points
 coordinate (P1) at ($(M1)+(30:1)$);
 coordinate (P2) at ($(P1)+(-30:1)$);
 coordinate (P3) at ($(P2)+(30:1)$); % aka N3

 % radius of white circles
 defRadius3pt+1.2pt % inner sep + ultra thick (sort of)

 % circle edge points for backgronund
 coordinate (n1) at ($(N1)+(225:Radius)$);
 coordinate (n2) at ($(N2)+(225:Radius)$);
 coordinate (n3) at ($(P3)+(45:Radius)$);

 % draw background
 % here we use the clip above (by using radius 10 in some relative coordinate additions
 % we also use that we are not using opacity != 1, so the bg can be made using two overlapping parts 
 beginscope[dunkelblau!80]
 fill
 ($(n2)+(-45:10)$)
 -- (n2)
 -- (N2)
 -- (M4)
 -- (M3)
 -- (M2)
 -- (M1)
 -- (P1)
 -- (P2)
 -- (P3)
 -- (n3)
 -- ++(-45:10)
 -- cycle
 ;

 % smaller shadow
 fill
 (n1)
 -- ++(-45:1)
 -- (0,0)
 -- (N1)
 -- cycle;
 endscope



 beginscope[white,ultra thick]
 draw (M1) -- (M2) -- (M3) -- (M4) -- (M5) -- (M6) -- cycle; 
 draw (M3) -- (N1);
 draw (M4) -- (N2);
 draw (M1) -- (P1) -- (P2) -- (P3);
 endscope

 % draw the circles
 fill[white] (N1) circle (Radius);
 fill[white] (N2) circle (Radius);
 fill[white] (P3) circle (Radius);

 node[white,below] at (-2,2) changefontpagbnDopamine;

 endtikzpicture
enddocument

Using iterative tricks you could obtain better result.

RESULT:

MWE:

documentclass[border=5pt,tikz]standalone
definecolorhellblauHTML129EB5
definecolordunkelblauHTML168DA3
usetikzlibrarybackgrounds
pagecolorhellblau
newcommandchangefont[3]fontfamily#1fontseries#2fontshape#3selectfont%Nice code!

begindocument
 begintikzpicture[
 %Environment styles
 kreis/.style=
 circle,
 fill,
 inner sep=3pt 
 
 ]
 node[white,below] at (-2,2) changefontpagbnDopamine;
 clip (-3,-1.5) rectangle (4,2);
 defDopamine(#1)[#2]
 beginscope[shift=(#1)]
 draw[line width=3pt,line join=round,#2]
 (30*11:1)
 -- (30:1)
 -- (30*3:1)
 -- (30*5:1)
 -- (30*7:1)
 -- (30*9:1)
 -- cycle
 (30*5:1)
 -- ++(30*5:0.5)node[kreis]
 (30*7:1) 
 -- ++(30*7:0.5)node[kreis]
 (30:1)
 -- ++(30:1)
 -- ++(-30:1)
 -- ++(30:0.5)node[kreis];
 endscope
 

 foreach x in 1,2,...,50
 Dopamine(x*0.05,-x*0.05)[dunkelblau]
 
 Dopamine(0,0)[white]

 endtikzpicture
enddocument

RESULT 2: Color Variation

Modify the lines 40-43

foreach x in 1,2,...,50
 Dopamine(x*0.05,-x*0.05)[black!x!dunkelblau]
 

Here is a solution that prevents you from doing things twice: defining the boundary of the dunkelblau area and drawing the thick white lines. This can be done using edge options with which you can draw single parts of a path with different styles. The hexagon is just a regular polygon which comes with shapes.geometric, and it is easier to work with relative coordinates ++ instead of xshift=1.71cm, I think. UPDATE: Followed Ruixi Zhang's suggestion to make the shadow tangent to the circle, flosed the gaps that were previously in, and made further simplifications. The actual diagram then boils down to four commands only.

documentclass[border=5pt,tikz]standalone
usetikzlibraryshapes.geometric,backgrounds
definecolorhellblauRGB18,158,181
definecolordunkelblauRGB22,141,163
pagecolorhellblau!60
makeatletter % https://tex.stackexchange.com/a/127045/121799
newcommandchangefont[3]fontfamily#1fontseries#2fontshape#3selectfont
tikzsetkreis/.style=fill=white,inner sep=3pt,circle,outer sep=0pt
pgfkeystikz/.cd, % https://tex.stackexchange.com/a/446026/121799
edge options/.code=tikzsetedge style/.style=#1,

pgfkeystikz/.cd,
opts/.code=
tikzsetedge style/.style=#1
pgfkeysalso#1,edge style/.style=


begindocument
 begintikzpicture[every edge/.append code = % https://tex.stackexchange.com/a/396092/121799 
 globalletcurrenttargettikztotarget % save tikztotarget in a global variable
 pgfkeysalsoappend after command=to[edge style] (currenttarget),
every edge/.append style=edge style ] 
 clip (-3,-1.5) rectangle (4,2);
 node[draw,regular polygon,regular polygon sides=6,minimum size=2cm,
 rotate=30,ultra thick,white,fill=dunkelblau!80] (poly) at (0,0);
 draw[ultra thick,white,line cap=round] (poly.corner 3) -- ++ (210:0.5) node[kreis] (k2) ;
 beginscope[on background layer]
 path[fill=dunkelblau!80] (poly.corner 2) 
 [edge options=ultra thick,white,line cap=round] 
 edge ++ (150:0.5) node[kreis] (k1) -- (k1.-135) -- ++(-45:1) -- cycle;
 path[fill=dunkelblau!80] (poly.corner 3) -- (poly.corner 4) -- (poly.corner 5) -- 
 (poly.corner 6)
 [edge options=ultra thick,white,line cap=round] edge (30:2) 
 edge ++ (-30:1) 
 edge ++ (30:1) node[kreis] (k3) 
 --(k3.30) -- (5,0) -- (5,-1.5) --++ (-5.5,0) 
 -- (k2.-135) --cycle;
 endscope
 node[white,below] at (-2,2) changefontpagbnDopamine;
 endtikzpicture
enddocument