I love the game, but 15$ for a Gleylancer-level port? This is steep.
Cotton 100% is basically Cotton 1 Arcade for kids. Yes, the difficulty isn't as brutal, the barrier is more persistent and extends are abundant, though you must uncover them since they're hidden pick ups. It's a cute game with good variation and amusing bosses. Including a skull doll.
The recommended tactic is... uh, since magic don't reload when you lose a life and only by defeating certain enemies, just use barrior and nothing else. Also the piercing fairy throw, hold the B button, is strong. When you need to pierce the walls, use it. This seems to be the last Cotton title that let you use the piercing fairy throw.
Be careful with the final boss. It's rather cheap! Push her towards the right part of the screen, she'll adjust her position automatically with yours, then when the thunder wall is being shot, pull back to the left and standby at bottom left, but give some room to evade the 5-way laser when she charges toward the left part of the screen.
This game is recommended for 1st time Cotton players before chewing the harder ones like Cotton 1 (Arcade and / or its ports) and Cotton Boomerang.