First commit of the starter kit.

assets/shaders/ui_error.frag

@@ -0,0 +1,18 @@
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_duration;
+uniform float u_time;
+uniform float u_time_end;
+uniform sampler2D texture;
+uniform bool is_shape;
+
+void main() {
+  if(is_shape) {
+    vec4 color = vec4(1.0, 0.0, 0.0, 1.0);
+    gl_FragColor = gl_Color * color;
+  } else {
+    vec4 pixel = texture2D(texture, gl_TexCoord[0].xy);
+    vec4 color = vec4(1.0, 0.0, 0.0, 1.0);
+    gl_FragColor = gl_Color * color * pixel;
+  }
+}

assets/shaders/ui_shader.frag

@@ -0,0 +1,29 @@
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_duration;
+uniform float u_time;
+uniform float u_time_end;
+uniform sampler2D texture;
+uniform bool is_shape;
+uniform bool hover;
+
+vec4 blink() {
+  if(hover) {
+    return vec4(0.95, 0.95, 1.0, 1.0);
+  } else {
+    float tick = (u_time_end - u_time) / u_duration;
+    float blink = mix(0.5, 1.0, tick);
+    return vec4(blink, blink, blink, 1.0);
+  }
+}
+
+void main() {
+  vec4 color = blink();
+
+  if(!is_shape) {
+    vec4 pixel = texture2D(texture, gl_TexCoord[0].xy);
+    color *= pixel;
+  }
+
+  gl_FragColor = gl_Color * color;
+}

assets/shaders/ui_shape_shader.frag

@@ -0,0 +1,12 @@
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_duration;
+uniform float u_time;
+uniform float u_time_end;
+
+void main() {
+  float tick = (u_time_end - u_time) / u_duration;
+  float blink = smoothstep(1.0, 0.5, tick);
+  vec4 color = vec4(blink, blink, blink, 1.0);
+  gl_FragColor = gl_Color * color;
+}