Welcome to the Feature Tour

This one course visits every kind of activity the engine can grade — all in your browser, all for free. Answer each station, watch the instant feedback, and your companion will cheer you on.

How this tour works

Every station is graded the instant you answer — no server, no account, no waiting.

• One activity at a time, graded right in your browser.
• A companion reacts to every pass and every miss.
• Your progress is saved locally — everything works offline.

When you answer a station, where is your answer graded?

Match each activity to what it grades

Tap a term on the left, then its match on the right.

Order the learn-by-doing loop

Reorder the steps into the correct sequence, then check.

• Read a short hook ▲ ▼
• Try the activity yourself ▲ ▼
• Get graded instantly in your browser ▲ ▼
• Read the kind feedback and continue ▲ ▼

Fill in how a station grades

Fill each blank, then check.

Every graded station binds a that decides your answer, and it runs in the choose… browsercloudserver .

The engine grades nine kinds of activity. Write SQL that returns HOW MANY there are.

A live decision: add headroom for Black Friday

Live architecture — watch the requests flow, then pick a strategy to see what changes.

Sort each activity by how you answer it

Tap an item, then the bucket it belongs to (or drag it). Then check.

Pick the pieces of a well-designed course

Tap the pieces that belong — leave out the ones that don't. Then check.

In one word: what makes this engine free to run?