ALllllright. I thought this was a pretty fun little game, but it has many errors.
I'll start with the good here, the riddles, I LOVED. Their simple, but I love having to actually decode stuff and have it be fun, so points to you there, but that may be me being biased.
The game was incredibly short, but you did a decent job of building up some nice suspense, but I felt like you leaned on having too short of a game too hard. Why not make more game, and just keep us guessing by not revealing too much information at a time?
I noticed an error in your decoding in the first diary entry you had to decode, You put "He's rcading" instead of "He's reading". Didn't notice any more errors throughout.
~~~ Super spoiler warning~~~
The dad trying to talk down the detective sounded like pure insanity. "Horrible, insane, mother"? Yea sure whatever. If that's what was intended, great on you, sounded like it. To accuse the mother would've been pretty insane, given the evidence. Overall, It left me wanting more, this score will probably increase in the coming games, but this is a nice start.