What is Hamas's game?
Notice that Hamas keeps shelling southwestern Israel relentlessly and is inviting and goading Israel into a fight. Hamas wants Israel to invade Gaza. Why? Some possible reasons:
1. Based on Israel's performance against Hizballah in Lebanon in 2006, Hamas is not deterred; it doesn't think Israel will defeat it in a confrontation, or at least that it, Hamas, will emerge in an acceptable condition without grave damage.
2. Hamas is coordinating with other actors like Hizballah, Syria, and Iran to turn an Israeli invasion of Gaza into a larger war involving some or all of those parties. In other words, Gaza is bait. (Not likely that Iran would want to get involved now before having nuclearized; unless, of course, it has already nuclearized.)
3. As in the parable of the scorpion who stings you even when it's to his own clear disadvantage, Hamas is a scorpion and cannot stop itself from attacking Israel whatever the rational, cost-benefit calculations.
4. Hamas is aware that Israel would defeat it militarily but counts on world opinion--meaning particularly the U.S., the EU, and the UN--to rescue it from an Israeli invasion that would inevitably cause harm and destruction to Gaza Arabs ("Palestinians").
All are plausible; the truth may lie primarily with one of them, or with some combination. What is ominous, and what Israeli policymakers and planners are presumably taking into account, is that Hamas wants this confrontation and does not fear it.