Stand on the floor tile that matches the planet symbol on the TV, three times in a row: in our playthrough it showed Venus, then Saturn, then Mercury, and the door opened after the third tile. The TV stays on static until you put two batteries in the remote on the table in Ivan's third-floor studio and press its only button, so the Tenebris Somnia TV puzzle starts upstairs.
Where do you find Ivan's remote control batteries?
One battery is in the second-floor apartment's bathroom and the other is in its kitchen. Grab both before you go back up to Ivan's studio.
Collect the first battery
Check the bathroom: bathtub with a curtain, toilet on the left, sink on the right.
Collect the other battery
The second one is in the kitchen, by the washing machine next to the refrigerator.
The remote won't work with one battery, so don't head upstairs after the first pickup or you'll be walking the stairs twice.
How do you activate Ivan's apartment TV remote?
Insert both batteries into the remote attached to the studio table, then press its single button. The remote stays on the table; return to it in Ivan's third-floor studio.
Install both batteries at the table
Interact with the remote on the foreground table. Julia's dialogue acknowledges that the batteries are installed.
Press the remote's button
Press the single button, then head back to the second-floor television. The remote interaction ends with Julia hoping its signal reaches downstairs.
What order do you step on the floor symbol tiles?
Step on whichever tile matches the symbol on the screen. Each time you get one right, the TV switches to the next symbol. We saw Venus, Saturn, Mercury, and the door opened after Mercury. If your TV shows something else, ignore our order and match the screen, because the rule is the same either way.
The tiles are spread around the couch: Mercury, Venus, Mars, Jupiter, Saturn and the Moon.
Venus is a circle with a cross underneath. You'll also see that symbol on a floor plate near the right side of the couch.
Saturn has a cross at the top with a curved stroke extending to the right. Its floor plate is toward the foreground, left of the couch.
Mercury has horns above its circle and a cross below. Its plate sits to the left of the television cabinet, close to the wall.
Pay attention to the top of the symbol when distinguishing Mercury from Venus. Both have a circle and a cross underneath, but Mercury adds the horns.
After the third tile the door opens and the TV screen cracks. The rest of the floor is in the Second Floor walkthrough.