Caps Lock
The Czech layout is QWERTZ with the accented letters ě, š, č, ř, ž, ý, á, í and é on the number row, so digits need Shift. Ů and ú have their own keys, while ď, ť and ň are typed with the háček dead key.
Take the test, then follow the lessons and the adaptive mode. The hint under the text shows when a dead key comes first and which finger presses each key.