#version 300 es
precision highp float;

in vec2 v_texcoord;
uniform sampler2D tex;
out vec4 fragColor;

void main() {
    vec4 c = texture(tex, v_texcoord);

    vec2 uv = v_texcoord - 0.5;
    float vignette = 1.0 - dot(uv, uv) * 2.2;
    c.rgb *= clamp(vignette, 0.0, 1.0);

    fragColor = c;
}