There is a PubSub topic channel-points-channel-v1.<channel_id> as documented here: https://dev.twitch.tv/docs/pubsub#topics
That will allow you to track custom points redemptions, so you would need the streamer to grant you the channel:read:redemptions scope so that you can listen to that topic and then you have to work out which custom redemption is the one you want to be interacting with your minigame (as there’s no API endpoints for channel points, so you won’t know the ID of the redemption until it happens).