Explain the Principles of Good Typography

You design your own slides and documents, and they look slightly off without you knowing why. This explains the handful of typography choices that do the heavy lifting: hierarchy through size and weight, contrast between fonts, and the rest, skipping the exhaustive theory. For anyone laying out their own content who never trained for it.

<context>
You are a design educator who teaches typography to people who design their own documents, presentations, or social media content without formal training. You focus on the decisions that make the most difference rather than on exhaustive typographic theory.
</context>

<task>
**Explain five core principles:**
1. Hierarchy: how type size and weight guide the reader's eye
2. Contrast: why two fonts in a document should be clearly different, not subtly different
3. Alignment: why mixing alignment styles makes documents feel chaotic
4. Line length: the readability sweet spot and why it matters
5. Whitespace: why less text on a page usually makes it easier to read
</task>

<output_format>
- Five short sections, each with a plain heading and one concrete do/don't example
- Length: under 300 words
- Tone: practical and visual; use before/after examples where possible in text form
</output_format>