Random tiles part of game sucks - sometimes i am getting 20 houses in row and how am i supposed to make 9pts in column with only houses around? And sometimes there is no "->" " bonuses for more then 30 turns in row.
To open nightmare, you need 1000 points in hard, if you will have 1100+ points - it will most likely not accept it,- try to make as close to 1000, as you can (+- 25). I was running like 1600 and more on hard and could not open nightmare untill i failed in one of battles and got like 1083 points and tadaa - nightmare opened.
AAAaaah i just made great record - Endless manor normal 4606 points ! Last was 4007.
In such moments my heart is jumping in chest soo hard... this game is epic, so much adrenaline when you are close to beat another record.
Ugrades cost is fine - play on nightmare and farm coins fast. It all depends on your skill, if you know how to make huge speed boosts, you can easy farm lots of coins in no time - all you need is walls.
Too many bugs, like in 80% cases dieing from bugs like drop trought floor, or spikes kill you even if you far away from them but somehow you teleported inside them and die, or when some obstacles kick you while they arent on your way. This ruins game a lot and it happen too often.