Chrono Boss Rush Version 2.0

1. Here are the changes to update the Level 3 Final Boss (The Eternal One) to use accurate hero weapons and to modify the screen shake effect for the Level 29 and Level 30 bosses to shake the ground instead.

2. The following changes add an "Expert" difficulty mode. This mode features 3.0x health (50% more than Hard mode's 2.0x), faster attack rates, and unpredictable behavior where bosses randomly speed up their attack timers or twitch/dodge. It is unlocked after beating Hard mode.

3. I've added a "Leaderboard" button to the main menu, which displays the fastest completion times. A timer will now be visible during gameplay, and upon completing a full set of levels, you'll be prompted to enter your name to save your score.