Played for a few minutes and already have a list of things that are getting in theway of enjoying this game.
1: Powerups, coins and dust from destroyed objects block bullets. This is one is bad with the enemies that split into 3 little things that charge at you, they come pushing the coins dropped by the larger one and simply get a cheap shield.
2: Enemies hiding behind walls due to the perspective. So early in the game and already getting cheap shotted by stuff popping behind walls.
3: Unlocking the RGB exit will automatically end the dungeon. Did the mistake of buying 20 mushrooms at once and had them bounce all over the room, while collecting the ones near the exit it opened due to me spamming E to get them all and the level ended with half of them still lying around on the room.