Enable files' drop area, two levels about the index

levels/time-machine/sequence

@@ -1,10 +1,13 @@
-conflict
 init
 checkout-commit
 branching
 merge
 branches
+conflict
 pull-push
 rebase
 reorder
 bisect
+steps
+split
+sandbox

levels/time-machine/split

@@ -0,0 +1,26 @@
+title = Split a commit!
+cards = checkout commit reset-hard reset add rebase-interactive rebase-continue show
+
+[description]
+
+Here, both changes happened in one commit! Split them to be in two commits instead.
+
+[setup]
+
+echo something > file1
+echo something else > file2
+git add .
+git commit -m "Initial commit"
+
+echo this should happen first >> file1
+echo and this should happen after that >> file2
+git commit -am "Both together"
+
+echo this is some other change >> file1
+echo this is some other change >> file2
+git commit -am "Something else"
+
+[win]
+
+test "$(git diff-tree --no-commit-id --name-status -r main^)" = "M	file2" &&
+test "$(git diff-tree --no-commit-id --name-status -r main~2)" = "M	file1"

levels/time-machine/steps

@@ -0,0 +1,23 @@
+title = One step after another
+cards = checkout commit reset-hard add
+
+[description]
+
+Sometimes, you might want to record the order in which things changed, instead of making a single commit.
+
+What happened here? Make two commits from the changes (using the "add" card), in an order that makes sense!
+
+[setup]
+
+echo something > file1
+echo something else > file2
+git add .
+git commit -m "Initial commit"
+
+echo this should happen first >> file1
+echo and this should happen after that >> file2
+
+[win]
+
+test "$(git diff-tree --no-commit-id --name-status -r main)" = "M	file2" &&
+test "$(git diff-tree --no-commit-id --name-status -r main^)" = "M	file1"