Learn German: Mein Puls rast, während ich durch den Flur schleiche. - My pulse races while I sneak through the hallway.

Während can be both a preposition meaning 'during' (which requires the genitive case) and a subordinating conjunction meaning 'while'. Here, it acts as a conjunction connecting two clauses. As a subordinating conjunction, it pushes the conjugated verb (schleiche) to the very end of its clause.

Why is it durch den Flur in the accusative case? Doesn't sneaking imply movement within a location, which would trigger the dative?

The preposition durch ('through') is a strictly accusative preposition. It always forces the following noun into the accusative case, regardless of context. Since der Flur (the hallway) is masculine, it becomes den Flur. You are likely thinking of two-way prepositions (like in or auf), which change case based on destination versus location, but durch does not belong to that group.

Is schleichen a regular or irregular verb?

Schleichen (to sneak) is an irregular (strong) verb. Its simple past form is schlich, and its past participle is geschlichen. Since sneaking inherently involves movement from one place to another, it requires the helping verb sein to form the perfect tense, as in Ich bin durch den Flur geschlichen (I sneaked through the hallway).

Can I use the verb rasen anytime someone is running very fast?