The Room 2 is 69p / 99c on iOS and Android and you should go buy that
Your credit card, if you've forgotten, is in your bedside drawer. But, darn, it's locked. The key, you seem to recall, is inside the wall safe. But you've forgotten the combination. You wrote it down. But where?
You scan the walls of your room, and notice one of your pictures is titled at an odd angle. You pry it off the wall, hastily turn it around, and see some strange lines on the back. What do they mean? What are they supposed to represent?
Then it hits you. You flip down your magic sapphire eyepiece to reveal a series of dots laid out on the lines. Of course - they're musical notes!
You dash over to the piano and start hammering out discordant noises. You really wish you paid attention in music class now because every damn adventure game features a musical puzzle. But you stumble through it, and on the last chime, a secret compartment opens on the back of the piano. Bingo.
Inside you find a book of matches. If you knew it was all working towards this you would have popped down to Tesco Express and picked up a lighter. But nevermind, we're making progress now.
You're drawn to the fireplace on the other side of the room. You've never lit it since moving in because this isn't the past and electricity exists now. But logic and years of playing point-and-click adventures would dictate that you need to start a fire with your matches.
The logs start to smoulder and suddenly the fireplace bursts into life. There's a roaring fire, and flames lick at the inside of the chimney. With the dark alcove now bathed in light, you can see that the numbers 4, 5, 2, and 1 are etched into one of the bricks.
That must be the combination you think, because that sort of thing makes sense in a puzzle game. You punch the numbers into the safe's digital lock, swing open the door, and - what's this? A sextant and a deck of tarot cards? Now things are getting interesting.
By this point, the sale has long been over and the game has returned to the full price of £1.99 / $2.99.