How do you make glass on little alchemy

How to make Glass:
Fire + Sand = Glass

Fire:
STARTER

Sand:
Stone + Air = Sand

Air=
STARTER

Stone:
Air + Lava = Stone

Air:
(see bolded part above)

Lava:
Fire + Earth = Lava

Fire:
STARTER

Earth:
STARTER

Also after you make glass you can make:

Glasses:
Metal + Glass = Glasses
Glasses + Sun = Sun Glasses
Glasses + Human = Nerd

Glass + Electricity = Lightbulb

Plant + Glass = Glasshouse

Sand + Glass = Hourglass