Reorder levels and chapters into a better sequence

levels/intro/checkout

@@ -0,0 +1,31 @@
+title = Getting the last version
+cards = checkout-file
+
+[description]
+
+You've been working on your essay for a while. But - ughh! Now your cat walks over your keyboard and "helps you", so now it's all messed up! :/
+
+But Git is here to help! To discard all changes your cat made, and go back to the version in the last commit, use `checkout`!
+
+[setup]
+
+echo "A" >> essay.txt
+git add .
+git commit -m "Initial commit"
+
+echo "B" >> essay.txt
+git commit -a -m "Improved version"
+
+echo "C" >> essay.txt
+git commit -a -m "Even better version"
+
+echo "D" >> essay.txt
+git commit -a -m "Marvelous version"
+
+echo "blarg
+blaaaargh" > essay.txt
+
+[win]
+
+# Restore the version from the last commit.
+cat essay.txt | grep D

levels/intro/checkout-commit

@@ -0,0 +1,44 @@
+title = Moving through time
+cards = checkout commit-auto
+
+[description]
+
+The yellow boxes are frozen points in time, we call them "commits"! You can travel between them using the "checkout" card! (Try it!)
+
+The grey panel below shows your current environment - click on an object to inspect or modify it!
+
+Can you find out what happened here? Then, come back to the latest commit, and fix the problem, using the "commit" card!
+
+[setup]
+
+mkdir room1 room2
+echo "A young girl with brown, curly hair." > room1/little_sister
+echo "This piggy bank belongs to the big sister.
+It contains 10 coins." > room2/piggy_bank
+git add .
+git commit -m "The beginning"
+
+mv room1/little_sister room2
+git add .
+git commit -m "Little sister walks over"
+
+echo "Has 10 coins." >> room2/little_sister
+echo "This piggy bank belongs to the big sister.
+It is empty." > room2/piggy_bank
+git add .
+git commit -m "Little sister does something"
+
+mv room2/little_sister room1
+git add .
+git commit -m "Little sister walks back"
+
+git checkout --detach
+git branch -d main
+
+[win]
+
+{ git show HEAD:room2/piggy_bank | grep "10 coins"; } && { git show HEAD:room1/little_sister | grep -v "10 coins"; } && { git rev-parse HEAD^; }
+
+[congrats]
+
+Wonderful! Now that you're getting familiar with the time machine, let's look at some more complicated situations...

levels/intro/first-remote

@@ -0,0 +1,39 @@
+title = Working together
+cards = pull commit-auto push
+
+[description]
+
+A friend has asked you to help with an essay about hobbies! She has already started to write a list, started tracking it in a Git repository. You can get a copy by using `git pull`!
+
+
+[congrats]
+
+"Thanks, these are some really nice hobbies! Hope we can do that together soon!"
+
+[setup]
+
+echo "~ Best hobbies ~" > hobbies.txt
+git add .
+git commit -m "Initial version"
+
+git push -u friend main
+
+[setup friend]
+
+git checkout main
+echo " 
+- Collecting stamps
+- Looking at clouds" >> hobbies.txt
+
+git add .
+git commit -m "Added two hobbies"
+
+[win]
+
+# Help her by adding at least two more items to the list! 
+test "$(cat hobbies.txt |wc -l)" -ge 6
+
+[win friend]
+
+# When you're done, commit your result and use `git push` to send it to her copy of the repository!
+test "$(git show main:hobbies.txt |wc -l)" -ge 6

levels/intro/init

@@ -0,0 +1,24 @@
+title = Welcome!
+cards = init
+
+[description]
+
+Welcome, time agent! Good to see you - we could really use your help with fixing some temporal paradoxes!
+
+Ready to initialize your time machine? Drag the `git init` card into the empty space above it!
+
+[setup]
+
+rm -rf .git
+
+[win]
+
+test -d .git
+
+[congrats]
+
+Oh hey, that's you! :)
+
+The time machine can help you fix problems in the past! It allows you to collaborate with other time agents! It's really powerful, and it's really popular!
+
+Let's get familiar with it! Click on "Next level", as soon as you're ready!

levels/intro/motivation

@@ -0,0 +1,53 @@
+title = Why Git?
+cards = file-copy
+
+[description]
+
+So you've been working on an essay about goldfish. You can look at the backup copies you made by clicking on them!
+
+But look - something went wrong in the latest version of the file! Maybe it has been infected with a vowel-eating virus?
+
+[congrats]
+
+Good that you had that backup, huh?
+
+But you're a bit worried that two weeks from now, you'll have hundreds of copies of your essay, and it will be hard to keep track of all of them.
+
+And especially when working with other people, sending backup copies around doesn't seem ideal.
+
+Let's look at another way to do this. :) Click "Next Level" as soon as you're ready!
+
+[setup]
+
+rm -rf .git
+
+echo "~ Why goldfish are the best pets ~
+
+(I still need to write this.)" >> essay1.txt
+
+
+echo "~ Why goldfish are the best pets ~
+
+- They don't make any noise.
+- They are pretty. (I should probably put this higher in the list?)" >> essay2.txt
+
+
+echo "~ Why goldfish are the best pets ~
+
+- They are pretty.
+- They don't pee on the carpet.
+- They don't make any noise." >> essay3.txt
+
+echo "~ Why gldfsh r th bst pts ~
+
+- Thy r prtty.
+- Thy dn't p n th crpt.
+- Thy dn't mk ny ns." >> essay4.txt
+
+[win]
+
+# Make a new version (with the number 5) from the last version that's still okay
+cat essay5.txt | grep carpet
+
+# And add at least two more lines to it!
+test "$(cat essay5.txt | wc -l )" -ge 7

levels/intro/restore

@@ -0,0 +1,28 @@
+title = Looking into the past
+cards = checkout-from
+
+[description]
+
+You've been working on your essay for a while. But you're not happy with the changes you've made recently. You want to go back to the version called "Best version"!
+
+No problem, you can use the `checkout` card to restore your essay from an older commit!
+
+[setup]
+
+echo "Initial version" > essay.txt
+git add .
+git commit -m "Initial commit"
+
+echo "Improved version" > essay.txt
+git commit -a -m "Improved version"
+
+echo "Best version" > essay.txt
+git commit -a -m "Best version"
+
+echo "Less-good version" > essay.txt
+git commit -a -m "Less-good version"
+
+[win]
+
+# For nostalgic reasons, restore the very first backup you made!
+diff essay.txt <(echo "Best version")

levels/intro/sequence

@@ -0,0 +1,5 @@
+motivation
+setup
+checkout
+restore
+first-remote

levels/intro/setup

@@ -0,0 +1,34 @@
+title = A better way
+cards = init commit-auto
+
+[description]
+
+One month later, you're woking on an essay about tardigrades!
+
+This time, a friend has recommended that you use the version control system Git to keep backups of your file.
+
+Currently, your directory only contains your essay. To initialize a Git repository in your directory, use the `init` card!
+
+Then, each time you want to make a backup, use the `commit` card!
+
+That way, you've made a backup of the current version of the file. 
+
+[setup]
+
+rm -rf .git
+
+echo "~ Why tardigrades are cool ~
+
+- They can survive in space.
+- They are resistant to extreme heat and cold." > essay.txt
+
+[win]
+
+# Initialize a Git repository
+test -d .git
+
+# And make another commit
+test -d .git && git rev-parse HEAD^
+
+# Add at least two more lines.
+test "$(git show HEAD:essay.txt | wc -l)" -ge 6