:root {
    --primary-color: #337ab7;
    --secondary-color: #ffffff;
    --background-color: #f7f9fc;
    --font-family: 'Roboto', sans-serif;
    --gradient-start: #8400ff;
    --gradient-end: #018c9e;
    --text-color: #333;
    --input-border-color: #ccd1d9;
    --input-focus-color: #5b9bd5;
    --button-hover-color: #017b8c;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

body {
    font-family: var(--font-family);
    background: linear-gradient(to right, var(--gradient-start), var(--gradient-end));
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

header {
    background: linear-gradient(to right, var(--gradient-start), var(--gradient-end));
    padding: 1.5em;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
}

header h1 {
    color: var(--secondary-color);
    margin: 0;
    font-size: 2.5em;
    font-weight: 900;
}

nav ul {
    display: flex;
    list-style: none;
    padding: 0;
    margin: 0;
}

nav a {
    color: var(--secondary-color);
    text-decoration: none;
    padding: 0 1em;
    font-size: 1.6em;
    font-weight: 700;
    transition: color 0.3s;
}

nav a:hover {
    color: #ffeb3b;
}

main {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: center;
}

.welcome-message {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    text-align: center;
    padding: 4em;
    background: rgba(255, 255, 255, 0.8); /* Yarı saydam beyaz arka plan */
    border-radius: 15px;
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
    backdrop-filter: blur(10px); /* Arka plan bulanıklığı */
    border: 1px solid rgba(255, 255, 255, 0.3); /* Hafif beyaz kenarlık */
}

.welcome-message h2 {
    font-size: 2.5em;
    color: var(--primary-color);
    margin-bottom: 1em;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.1);
}

.phone-number-input {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 100%;
    max-width: 400px;
}

.input-wrapper {
    display: flex;
    width: 100%;
    margin-bottom: 1em;
    border: 1px solid var(--input-border-color);
    border-radius: 8px;
    overflow: hidden;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.phone-number-input select,
.phone-number-input input {
    padding: 1em;
    border: none;
    font-size: 1.1em;
    outline: none;
    transition: border-color 0.3s, background-color 0.3s;
}

.phone-number-input select {
    background-color: var(--secondary-color);
    border-right: 1px solid var(--input-border-color);
    appearance: none; /* Remove default arrow icon */
}

.phone-number-input input {
    flex: 1;
    border-left: none;
    border-top-right-radius: 0;
    border-bottom-right-radius: 0;
}

.phone-number-input select:focus,
.phone-number-input input:focus {
    border-color: var(--input-focus-color);
}

.phone-number-input button {
    padding: 0.75em 1.5em;
    border: none;
    border-radius: 8px;
    background: linear-gradient(to right, var(--gradient-start), var(--gradient-end));
    color: #fff;
    font-size: 1.2em;
    font-weight: bold;
    cursor: pointer;
    transition: background 0.3s, transform 0.3s, box-shadow 0.3s;
}

.phone-number-input button:hover {
    background: var(--button-hover-color);
    transform: scale(1.05);
    box-shadow: 0 8px 16px rgba(0, 0, 0, 0.2);
}

.phone-number-input button:focus {
    outline: none;
}

/* Ekran boyutlarına duyarlılık */
@media only screen and (max-width: 768px) {
    .welcome-message h2 {
        font-size: 2em;
    }

    .phone-number-input {
        flex-direction: column;
        width: 100%;
    }

    .input-wrapper {
        flex-direction: column;
    }

    .phone-number-input select,
    .phone-number-input input,
    .phone-number-input button {
        width: 100%;
        margin-bottom: 0.5em;
    }

    .phone-number-input button {
        margin-left: 0;
    }
}