Python in a game

I have had multiple ideas for awesome games,but not knowing python has held me back. So i learned some python and i know the basics now, but when i get in the game engine I am lost. I’ve looked everywhere and there are no tuts on how to make a game in blender using python so that i can learn some blender python stuff.So what i want to know is how do i write scriptslike these SCRIPT IDEAS below AND apply them to objects or whatever: Ex
1.if bobby steps on this box,send him to this place
2.if ammo is empty, auto reload the gun,if no ammo,write no ammo
3.making a clickable button that starts the game or anything,like options
4.if the button E is pressed then play “this animation” or “start this script” or go to “this cutscene”