Hi Toni,
Yeah you can watch games that have been played earlier ( although there is a time linit on doing so,they probably take up space on the server! just look at the list of all games and select a game you want to replay, at the top of the screen where you normally see " Join " or Watch ( Join when a game is waiting for players or watch to watch a game that is currently in play) you will see the option to replay click on that and you can watch the game replay, using the controls on screen you can watch it run or step through the game step by step.
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With regard to land walking there aren't any cards that give u protection against creatures that have it so you'll have to go after the creature itself,destroy it ( in white you have sunlance to deal 3pts of damage other colours have more options for this red/black spring to mind) you already use oblivion ring you also have temporal isolation (and in Extended faiths fetters) there may be other but those are the ones that quickly spring to mind.
As for artifact destruction in white you haven't any in green you would have naturalise and in red a few options ancient grudge, smash ( destroy artifact and draw a card) and from shadowmoor smash to smithereens.
Anyway i hope this reply helps you with card selection ( artifacts aren't a major problem in std (as there aren't that many played ) but can be in fut ext ( affinity is still big there) but remember whatever cards you choose to deal with artifacts ( unless like oblivion ring it can be used against other targets) is a dead card if the said threat doesn't arise. Anyway no matter what cards are played enjoy your magic
Regards
Harry