The site is now ready for the EU General Data Protection Regulation (EU-GDPR) and will therefore continue to operate even when the law is finally implemented. No personal data (including IP addresses) is stored any longer and a link to the privacy statement can be found at the bottom of every page (see below).
For now, all interactive parts of the site (like the IQ fact generator, the function plotter, and the Klong tutorial) have been removed, though. Maybe they will re-appear when the dust has settled and we understand the implications of the GDPR a little better.
Thanks to my webhoster who was very helpful while solving the problem and to everybody who mailed and offered help and support!
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