Raptor, very much a classic vertical scrolling game and one of my personal favorites for over 15 years years now. All the game is is straight up, high intensity action whereupon the player faces many waves of bad guy cannon fodder using an assortment of many weapons available. Depending on the difficulty, the player can face massive waves all throughout every level, allowing for effective difficulty scaling. The array of weapons is actually quite diverse, from simple machine guns, to missiles, bombs, lasers, turrets and quite a few others. Beauty of that is that if the player has enough money, they can purchase ALL of them, and switch between them. Speaking of purchasing, the player acquires money from destroying anything in missions, money which is used for buying new weapons, replenishing “health” and buying bombs.
The levels are separated into three “sectors” consisting of 10 missions that each bring different challenges, each more difficult than the previous, but more rewarding. While each individual level in each sector cannot be selected to be replayed, they are typically kinda short and each sector can be replayed as many times as the player wishes. While short levels may sound like a downside, the player's survivability is not all the high, especially in later levels, making short levels very much needed. Now here's the interesting part: despite the fact that the levels replayed are the same, I have always found them to be very repayable.
The downside to this game is not so much the game, but an issue that arose from being ported to windows. The controls, outside of the mouse, only function at half speed, so the player is only moving at half speed. The mouse isn't effected by this, but has some trouble getting to the far right side of the screen, but there's not typically a lot to do there, so it's not a big deal.
All in all, I have enjoyed this game for approaching 20 years now, and I highly recommend it, as long as you use mouse controls.