diff --git a/README.md b/README.md
index f93285a..42a043d 100644
--- a/README.md
+++ b/README.md
@@ -3,10 +3,12 @@
 This library is a customizable 2D math rendering tool for calculators. It can be used to render 2D formulae, either from an existing structure or TeX syntax.
 
 ```latex
-\frac{x_7}{\left\{\frac{\frac{2}{3}}{27}\right\}^2}
+\frac{x^7\left[X,Y\right]+3\left|\frac{A}{B}\right>}
+     {\left\{\frac{a_k+b_k}{5!}\right\}^n}
++ \sum_{k=1}^nk(-1)^k
 ```
 
-![Sample image](https://framapic.org/v4ODO95ftSAV/szXvX2amwuUN.png)
+![Sample image](https://framapic.org/MGABuOpMUDxn/duzY5eaLNVTj.png)
 
 ## Features
 
@@ -21,6 +23,8 @@ List of currently supported elements:
 * Fractions (`\frac`)
 * Subscripts and superscripts (`_` and `^`)
 * Grouping parentheses, brackets and braces (`\left` and `\right`)
+* Grouping angle brackets, vertical lines, and dots (invisible)
+* Summation symbols
 
 Features that are partially implemented (and what is left to finish them):
 
diff --git a/src/classes.c b/src/classes.c
index fd9af50..6c2a05e 100644
--- a/src/classes.c
+++ b/src/classes.c
@@ -118,6 +118,8 @@ void leftright_size(struct TeX_Node *node)
 
 	if(node->subtype == '<' || node->subtype == '>')
 		node->width = TEX_LEFTRIGHT_ANGLE_WIDTH;
+	if(node->subtype == '|')
+		node->width = 1;
 }
 
 void leftright_render(struct TeX_Node const * node, int x, int y, int color)
@@ -183,6 +185,10 @@ void leftright_render(struct TeX_Node const * node, int x, int y, int color)
 		TeX_line(x + w - 1, y + l, x, y, color);
 		TeX_line(x + w - 1, y + l, x, y + h - 1, color);
 		break;
+
+	case '|':
+		TeX_line(x, y, x, y + h - 1, color);
+		break;
 	}
 }
 
diff --git a/src/platform/sdl2.c b/src/platform/sdl2.c
index c521565..6c2df8d 100644
--- a/src/platform/sdl2.c
+++ b/src/platform/sdl2.c
@@ -117,7 +117,7 @@ static void init(void)
 	if(SDL_Init(SDL_INIT_VIDEO) < 0) fail("failed to initialize SDL");
 
 	int c = SDL_WINDOWPOS_CENTERED;
-	w = SDL_CreateWindow("2D rendering", c, c, 256, 128, 0);
+	w = SDL_CreateWindow("2D rendering", c, c, 320, 240, 0);
 	if(!w) fail("cannot create SDL window");
 
 	r = SDL_CreateRenderer(w, -1, SDL_RENDERER_ACCELERATED);
@@ -161,9 +161,9 @@ static void fini(void)
 int main(void)
 {
 	char const * formula =
-	"\\frac{x_7}{"//\\left<X,Y\\right>+3\\left<\\frac{A}{B}\\right>}{"
-		"\\left\\{\\frac{\\frac{2}{3}}{27}\\right\\}^2"
-	"} + \\sum_{k=1}^nk";
+	"\\frac{x^7\\left[X,Y\\right]+3\\left|\\frac{A}{B}\\right>}{"
+		"\\left\\{\\frac{a_k+b_k}{5!}\\right\\}^n"
+	"} + \\sum_{k=1}^nk(-1)^k";
 
 	struct TeX_Flow *flow = TeX_parse(formula);
 	if(!flow) { puts("parsing error!"); return 1; }