diff --git a/TeX/jam.sty b/TeX/jam.sty
new file mode 100644
index 0000000..bf07ec4
--- /dev/null
+++ b/TeX/jam.sty
@@ -0,0 +1,16 @@
+% square lattice (width #1, height #2, origin #3, spacing #4)
+\def\grid#1#2#3{
+  \foreach\i in {0,...,#2}{
+    \draw#3++(0,\i)--++(#1,0);
+  }
+  \foreach\i in {0,...,#1}{
+    \draw#3++(\i,0)--++(0,#2);
+  }
+}
+
+
+% cross (color #1, position #2)
+\def\cross#1#2{
+  \fill[color=#1]#2++(0.5,0.5)--++(0,1)--++(-1,0)--++(0,-1)--++(-1,0)--++(0,-1)--++(1,0)--++(0,-1)--++(1,0)--++(0,1)--++(1,0)--++(0,1)--++(-1,0);
+  \draw[color=black]#2++(0.5,0.5)--++(0,1)--++(-1,0)--++(0,-1)--++(-1,0)--++(0,-1)--++(1,0)--++(0,-1)--++(1,0)--++(0,1)--++(1,0)--++(0,1)--++(-1,0);
+}