This report contains observations regarding the Sparky bot. I have lost no coins or anything, nor am I bothered by having lost any games because of these observations.

1. When Affectionate Indrik enters, it immediately battles most powerful creature, when battling another creature would ensure Indrik's survival and actually remove an opponent's creature. Also, it always fights, even when there's nothing to gain from it, resulting in the loss of Indrik but no loss of opponent's creature.
2. Sparky used a 0/5 wall to block a 3/3 creature instead of 1/3 toxic insect, resulting in the loss of the game that turn. If the 3/3 had got through, the game would have continued.
3. When blocking, often doubles the blockers even though one would stop all damage, and multiple blockers don't actually kill attacker. And Sparky will often use all her creatures to block a single attacker, thus resulting in the end of the game since other creatures get through without being blocked. At other times, Sparky will not block with one or more of her creatures, resulting in the end of the game.
4. Sparky will often attack with her creatures even though the total damage to the player is minimal, thus having no creatures to block the player's next attack, resulting in the end of the game. If Sparky had kept back her creatures as blockers, the game would continue.
5. Last turn of the game and Sparky does not block when she has a creature (or multiple creatures) to do so, thus losing the game without bothering to block when she can. Sparky seems more interested in saving her creatures than blocking enough attacking creatures to keep the game going.
6. Sparky doesn't seem to take into account "protection against color" and will use multiple creatures to block, the multiple adding up to an amount that would normally kill the attacker.
7. Sparky does not seem to understand indestructible, meaning Sparky will use multiple defense creatures to try to kill such a creature to no avail, thus causing Sparky to lose creatures she does not need to lose.
8. Sparky does not seem to understand double-strike, meaning Sparky will defend with enough creatures to kill a non-double-strike creature but not enough to actually kill the attacking creature.
9. When Sparky is playing Red and is going to use Shock, there is a delay that gives away that fact. After playing my mana, I can click Next to see if Sparky will use it before I play a creature card. If Shock will be used, there is a longer delay than if Shock is not going to be played. (I wonder if black's Compound Fracture works the same way, but I have so far not had an instance when I could detect it.)
10. Also with Shock, Sparky usually delays using it until the end of the player's turn, even though using it earlier would block many things. Example: Elvish Archdruid is 2/2 and could be stopped with Shock. But because Sparky delays using Shock, Elvish Archdruid can be upped to 3/3 (or higher) using other Elf creatures that give +1/+1.
11. With Manifest Dread, the face-down card is placed next to other creatures that are the same, which gives away what creature is hidden/face down.
12. Sparky will always turn over face-down cards, even when doing so makes the creature have less power/defense.
13. Sometimes Sparky will attack with a 0/* creature (Armored Whirl Turtle), even when it can be destroyed by defenders.
14. Sparky will frequently attack with creatures that can easily be killed by a single defending creature.

I can provide images (or maybe video) of some of these if you need to see them.

SUGGESTION: Create a second "smarter" Sparky bot to play against players who want more of a challenge but do not want to play live players. I for one cannot play other live players, as the minor stress sometimes causes my cardiac fibrillation to start up. (I frankly cannot explain why playing a bot does not cause me stress while playing a live player does, but live players do stress me. I know: weird.) Usually such a fibrillation episode is not bad, but I cannot take that risk, since my fibrillation has ended me up in the hospital twice (but so far not from playing Magic). I very much enjoy playing Magic the Gathering Arena, and I would like more of a challenge by the bot. It seems you could simply make the "rules" that govern Sparky a bit different while still keeping the same decks. Better yet, give Sparky better decks. Maybe even make two more Sparky bots, one that challenges players very strongly and another that plays in between the teaching/beginner Sparky and the super-advanced Sparky.