Eww, yuck, ugly, bad! Well not that bad but still ugly! - Tracks should be either at 0deg, 90deg or 45deg, no other angles if at all possible. Where tracks make a 90 degree bend, put a 45 degree fillet in the corner. This goes for where they meet at a T intersection too. - Allow at least a 3mm clearence around mains tracks and especially around mounting holes. Also 2mm between the edge of the board and any tracks. - check the distance between D1 and the relay and R2 and transformer. It looks a bit close to me - Two tracks under U3 is possible but can make things tight and difficult. Best avoided unless necessary. - move R2 across and up a bit to allow more space around the tracks. - move the RX up to allow rome for R2 moving, relocate antenna track. - check the link under U3, it looks like it touches the other pins. - leave a reasonabe gap around the pads not connected to the ground plane. They look a bit small but it is hard to tell. - leaving an unused pin on the connector between the relay and mains is actually good practice. imagine getting a low voltage wire to the relay one position too far across. Excuse the MSpaint CAD attempt.
Making the layout look good is only.. so the layout will look good, some kind of electronics engineer code of conduct or something. Unless you are working with sensitive HF or extreme currents, you can route your traces whatever way you want. Spell your name with the relay driver lines or something
Sticking with regular angles is just good design practice. Electronically it won't make much distance, the fashon in the 70s was to go for curves but they are much harder on the design software. One area it can make a difference is where there are multiple tracks closely spaced. Couple that with aliasing (jaggies) and you can get hairs forming between tracks when it is etched. Putting fillets at the corner of tracks helps mechanically as sharp corners are prone to lift off the board when heated or stressed. The length of a trace doesn't matter too much, within reason. Exceptions are high frequency and high current. It is also good practice to keep mains and high voltage well away from low voltage areas and as close to the edge of the board where they originate as practical. The idea is to keep the nasty stuff in one area. The link between the receiver and HD12 shouldn't matter too much. From what I read the rx does all the RF work and gives out the original data stream so it is fairly low speed. Feel free to double check me though! Just noticed one other thing I missed. Remove the extra copper from under the transformer, around the mains connections, terminal strip and relay. If you get a stray mains wire you don't want it hitting any of the low voltqge stuff. Advise from a PCB manufacturer http://airborn.com.au/ Hope this all helps.
