Question
I am a shopkeeper who sells food to sorcerers on a corner shop in the city of Monte Lacum. How can I stop Ice Sorcerers breaking into it and stealing the food?
Attempts to prevent being stolen from
I tried to put a PIN code on the iron door one night. The next morning, I found that an Ice Sorcerer had created layers of ice around the PIN lock and smashed it to bits. I have only 700 royals in savings (enough to pay an Air sorcerer for 1 week's guarding). Oh, also everyone within 1km wants to go to my shop for food because it sells Extra Energy Food (EEF) that provides a much higher calorie-to-content ratio.
Background
*'*Set in 13th century Europe**'
Everyone is a sorcerer, specialising in one of the elements: Air (can fly), Earth (can cause earthquakes), Fire (can shoot fireballs), Water (can cause tidal waves), Light (can temporarily blind people), Dark (can send out their shadow), Life (can use the power of all living plants and animals nearby, excluding humans), Ice (freezes things - see above), Lightning (casts lightning - Emperor Roberto II is one), Shockwave (casts a shockwave), Metal (can shape metal - used by blacksmiths) and Null (partially immune to sorcery - used by people like me).
I have worked out how to trap all other types of sorcerers.
There are pets, yes (I have a dog named Terrar) but that isn't important.
Monte Lacum is a big draw for Earth, Water and Ice sorcerers (and Air ones, to a lesser degree).
My shop is like a supermarket, but without the non-food items.
Summary
I have nearly no money and am looking for ways to protect my shop (for more than 1 week - see above).