Shine a spotlight over a scene in GameMaker

fx_spotlight - Alarm 0

self.fadeIn += fadeStep;
if(fadeIn < fadeMax) {
    alarm[0] = fadeSpeed;
}

fx_spotlight - Create

self.fadeSpeed = room_speed / 15;
self.fadeIn = 0;
self.fadeStep = 10;
self.fadeMax = 140;
self.spot_surface = surface_create(room_width, room_height); // Will be erased if video memory reclaimed
self.alarm[0] = self.fadeSpeed;

fx_spotlight - Draw End

draw_surface_ext(self.spot_surface, 0, 0, 1, 1, 0, c_white, 0.9);

fx_spotlight - Step

surface_set_target(self.spot_surface);

draw_rectangle_color(0, 0, room_width, room_height, c_black, c_black, c_black, c_black, false);
draw_set_blend_mode(bm_subtract);
draw_circle_color(self.x, self.y, (room_width / 2) - self.fadeIn, c_white, c_white, false);

draw_set_blend_mode(bm_normal);
surface_reset_target();