How do i stop my kittens running out the door?

Hello,
I'm new to this site so sorry if there has been another similar thread already.
I have two 9 month old indoor kittens. They are very curious & playful, their latest thing is they both run out the front door as soon as I come home. During the day isn't so bad because I can see them & it's pretty safe but after dark I can't see where they go, they tend to wander round the small patch of grass in front of our house & hide under the hedge when I try to bring them back in. I worry because there is also a main road in front of our house and there are also a few foxes who also sometimes hide in the same hedge my kittens go to.
I just wanted to highlight the dangers before people start thinking I am cruel for not letting them outside.
We have a back garden which I do take them to... trouble is we have to go out the front door to the back of the house to access the garden.
Does anyone have any ideas how I can open my front door without the kittens running out?

Are they fixed?

Yes they were both neutered at 4 months. It is more of a curiosity thing. When I get them back in they dont meow to go back out, they carry on playing etc. I close the kitchen door when cooking and the bathroom door when running a bath and they both want to get in the rooms because the doors are closed. It isn't just down to them wanting to be outside

I was rushing my post as I was at work. My kittens always want to be involved in everything so it's more of a game for them to run out the door when we open it rather than the issue of them wanting to be outside. When I am in the bath they meow outside and claw at the door, i did let them in once and one jumped in the bath I also keep them out of the kitchen when i am cooking and its the same thing, they meow and watch through the glass panels on the door. Now when they hear the front door opening they just want to run out which is becoming very stressful for me when its dark, i worry about them getting lost or harmed. They are very playful, everything is a game

Yes, that makes sense!

Can you describe your play with them in the house?

Until they learn better I'd get some ping pong balls at the dollar tree and keep them in your car. When you get home open the door big enough to toss a ball in. The kitten should chase the ball into the house and clear the way for you to enter. A small ziploc baggie of cat treats would also work but gotta watch calories there. You can also keep some small toss toys or treats near the door so when you go out you can do the same thing.

Eventually they will learn their boundaries and stop trying. And maybe if you start tossing toys they will stay further back to better chase the toys. I did this with my cats (sorta different, more along lines of treat training as kittens for name and behavior). But all I have to do is pop the top on their treat jar and they go almost exactly 5 feet away from me for tossing distance. So you may see a similar affect when the door is opened once they associate door with toy or treats being tossed.

Thank you Kieka that is helpful, they do love ping pong balls
Talkingpeanut their favourite games are playing with ping pong balls, when its the 2 of them playing they run around chasing and batting the balls around. When I play with them they love it when i throw the ball and they jump and bat it then chase it around. The other thing they love is chasing a shoelace. Simba even brings the shoelace to me in his mouth and drops it by me when he wants to play. I always do it. They also love toy mice, fishing rod toys, they do like the laser pen too but i have reduced using that since i read somewhere that it frustrates cats (because they cant actually catch it they dont feel satisfied or something) I always entertain them when I am home I know how important it is for bonding and of course as they are indoor cats. I do take them into our back garden regularly and they enjoy chewing the grass, exploring and chasing eachother. When they turn 1 next year in the spring I will start to let them out. Its just at the moment its not safe

I just put some clothes away in my wardrobe, as soon as i opened the wardrobe they both jumped in and they are both sitting inside purring away. This is what they are like all the time They get involved in everything its adorable. I am just trying to give an idea of their personalities. They are very affectionate and often sit with me/on my lap purring. They are very happy kittens