#version 330 core
layout(location = 0) in vec3 aPos;
layout(location = 1) in vec4 aColor;
layout(location = 2) in float aLife;
layout(location = 4) in float size;

out vec4 vColor;

uniform mat4 uMVP;
uniform float uScreenHeight;

void main() {
    float alpha;
    if (aLife < 0.0) {
        alpha = 1.0;               // immortal — fully opaque
    } else {
        alpha = clamp(aLife / 2.0, 0.0, 1.0); // fade over last 2 seconds of life
    }

    vColor = vec4(aColor.rgb, aColor.a * alpha);
    vec4 clip_pos = uMVP * vec4(aPos, 1.0);
    gl_Position = clip_pos;

    float base_size = 0.5 + (size * 2000);
    gl_PointSize = max(1.0, base_size / clip_pos.w);
}