Here's some things that i've done.

• Shadows and lighthing.
• Inventory (Pick items, use them).

• Keycards.

• Doors (Button and keycard).

• SCP-173 (Blinking system and random appear).

• SCP-294 (With 21 liquids/materials to drink).

• SCP-049.

• SCP-066.

• SCP-009.