Some more info :
About the delta wing resemblance, Mirage 2000 is based on a pure delta wing design while Tejas has a compound delta wing, which is sometimes referred to as cranked delta due to crank visible from an angle.
Tejas sports an all digital digital Fly-by-wire control system while Mirage 2000 makes use of an Analog Fly-by-wire control system
Mirage 2000 has a cone in it’s inlet ,called the mouse, which is active and regulates air flow into the inlet at different speeds. Hence Mirage 2000 can achieve Mach 2.2 without damaging it’s turbine blades while Tejas doesn’t sport any movable mechanical parts. This restricts it’s top speed to Mach 1.8.But lack of movable parts help in cutting down maintenance time, an advantage for Tejas to act as an interceptor/point defence role.
Tejas has Y-shaped intakes to hide the blades, which help in reducing the frontal RCS of the aircraft. Remarkable fact is RCS of Tejas is 1/6rd of Mirage 2000.
Both are different designs with different avionics. Inspiration is one thing, copying/reverse-engineering is another thing. In development of Tejas, ergonomics was not considered otherwise HAL would have gone for a Mig-21 design, like PAC/CAC developed JF-17,whose origins lie in Mig-21 designs.