Assumed environment: `de.markusfisch.android.shadereditor`

star-blob.glsl

#version 300 es
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif

uniform vec2 resolution;
uniform float time;
out vec4 fragColor;

float angle(const vec2 x, const vec2 y) {
	vec2 offset = y - x;
	return atan(offset.y, offset.x);
}

const float PEAKS = 5.0;

void main() {
	float m = min(resolution.x, resolution.y);
	vec2 uv = gl_FragCoord.xy / m;
	vec2 CENTER = resolution / m / 2.0;

	float shape = sin(
		// rotation
		sin(time) * PEAKS * 2.0 +
		angle(uv, CENTER) * PEAKS
	) / 4.0
	// polarity inverter
	* sin(time * 2.0) / 4.0;

	// size bounce
	float radius = (sin(time * 1.25) + 4.0) / 16.0;

	vec3 col = vec3(0.5, 0.8, 1);
	// no anti-alias
	if (distance(uv, CENTER) + shape < radius) {
		col = vec3(1.0, 1.0, 0);
	}
	fragColor = vec4(col, 1);
}