Visually, the game is a mixed bag. Some of the sprites are very nice drawings, others look like they were done in MS Paint in five minutes. I'm actually okay with either style, but it's not consistent here and I'm not sure what aesthetic the game is going for overall. The music is fun and fits the game well and the sound effects work pretty good, too.
Using the themes as weapons is a creative idea, and I think it fits the overall mahou shoujo feel well. The sweet definitely looks like a sweet, but the smile feels like a bit of a stretch- it looks more like a boomerang or generic energy wave.
I'm not really a fan of the automatic shooting with fixed cooldown. I found it almost impossible to keep track of the cooldowns while also dodging enemies and lining up shots. It is something that makes the game stand apart, though, and I think abandoning it would be going too far. I think just speeding up the cooldowns so missing one has less impact would help a lot. Moving the indicators to the magical girl itself so that they're in my field of view would help, too. I'm not sure if the cooldowns for smile and sweet are synchronized, but they should be.
The difficulty curve is a bit steep for my liking, but it's not horrendous, and I think a lot of players will find it just right. I do wish leveling was a little faster, just to break things up a little, even if the improvements each level were weaker.
I found that every wave inevitably devolved into circle-strafing the enemy, which seems to happen for top-down wave shooter. This is definitely not a good thing, but I'm not sure what can be done about it.