Well I never thought I'd actually pay for an alarm but the time has come because my phone broke and I needed an alarm clock in a pinch. Well first of all it's a very basic app you can make Mario jump as he runs continuously across the screen and once you gain 100 coins you change into Luigi and also there's a mushroom that you can get that makes mario grow or shrink. Also I suggest if you're using it for it's alarm feature you mute your 3DS on the side volume because I believe every hour or so it goes off and makes a 1up sound.
Now moving on to the alarm it's really basic and easy to use. , you have a few slots for setting multiple alarms, you have 3 songs you can use for an alarm 1) The main Mario theme 2) The invincible star theme and the under water theme. Also it can over ride the main volume that way you can mute your 3DS and it'll still go off and to my surprise the volume was reasonably loud. However if you're the type who needs several alarms and the sound of a fire alarm and still barely manage to get up then this alarm is not for you. However if you're the average sleeper or a light sleeper then this alarm clock is quite nice if you place it close to you., as for across the room results may vary.
I keep mine on the charger but if you don't have a charge on you then you can put it on energy saving mode, turn off wifi and have brightness at 1 and it should last you for the night. However you can also shut your 3DS and the alarm will still go off. Now there's one more thing I can talk about there's a snooze feature if you turn that on you tap the screen and it'll snooze if not it'll keep going and in order to turn the alarm off the alarm with out the obvious like your 3DS dying and such is you hold down the (A) button for a certain amount of time.
Now is it a permanent replacement for an alarm? was it worth $2 ? I would say no but if you're in a pinch like me and need an alarm then it works as a temporary solution! So I'll be using this method until I can replace my phone or I go out and buy a real alarm clock.