// shaders
static const char *vertex_shader_source =
"#version 100 \n\
+precision mediump float;\n\
+precision mediump int;\n\
attribute vec2 position; \n\
attribute vec3 color; \n\
varying vec3 frag_color; \n\
}";
static const char *fragment_shader_source =
"#version 100 \n\
+precision mediump float;\n\
+precision mediump int;\n\
varying vec3 frag_color; \n\
void main(void) \n\
{ \n\