* {
    box-sizing: border-box;
    user-select: none;
    -webkit-user-select: none;
}

body {
    background-color: #0d0d0d;
    color: #fff;
    font-family: 'Courier New', Courier, monospace;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
    padding: 10px;
}

.cdu-container {
    background: linear-gradient(145deg, #2d3037, #1f2125);
    width: 100%;
    max-width: 390px;
    padding: 18px;
    border-radius: 20px;
    box-shadow: 0 15px 35px rgba(0,0,0,0.9), inset 0 1px 2px rgba(255,255,255,0.15);
    border: 4px solid #141517;
}

/* Ekran Çerçevesi ve Ekran */
.screen-frame {
    background-color: #030303;
    border: 3px solid #3a3a3a;
    border-radius: 10px;
    padding: 8px;
    margin: 10px 0;
    box-shadow: inset 0 0 15px rgba(0,255,100,0.1);
}

.screen {
    background-color: #000;
    color: #00ff66;
    height: 230px;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    font-weight: bold;
    font-size: 13px;
    letter-spacing: 1px;
    text-shadow: 0 0 3px rgba(0, 255, 102, 0.5);
    padding: 4px;
}

.screen-header {
    display: flex;
    justify-content: space-between;
    border-bottom: 1px solid #004411;
    padding-bottom: 4px;
    color: #ffffff;
    font-size: 14px;
}

.screen-body {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.screen-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.scratchpad-area {
    border-top: 1px solid #004411;
    padding-top: 4px;
    color: #ffffff;
    font-size: 15px;
    min-height: 22px;
    word-break: break-all;
}

/* LSK Tuşları (Ekran Yanı Tuşlar) */
.lsk-group {
    display: flex;
    flex-direction: column;
    gap: 14px;
    justify-content: center;
}

.btn-lsk {
    background: linear-gradient(145deg, #444, #222);
    color: #888;
    border: 1px solid #111;
    width: 32px;
    height: 28px;
    border-radius: 4px;
    cursor: pointer;
    box-shadow: 0 3px 0 #111;
    font-weight: bold;
}

.btn-lsk:active {
    transform: translateY(2px);
    box-shadow: 0 1px 0 #111;
    background: #222;
}

/* Klavye Alanı */
.keyboard {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-top: 10px;
}

.function-keys {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 5px;
}

.alpha-num-section {
    display: flex;
    gap: 8px;
}

.num-pad {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 5px;
    flex: 1;
}

.alpha-pad {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 4px;
    flex: 1.8;
}

/* Genel Tuş Tasarımları */
button.key {
    background: linear-gradient(145deg, #383b42, #212328);
    color: #ececec;
    border: 1px solid #141517;
    padding: 9px 0;
    font-size: 11px;
    font-weight: bold;
    border-radius: 5px;
    cursor: pointer;
    box-shadow: 0 3px 0 #121315, 0 3px 4px rgba(0,0,0,0.4);
    touch-action: manipulation;
}

button.key:active {
    transform: translateY(2px);
    box-shadow: 0 1px 0 #121315;
    background: #18191c;
}

button.func-key {
    background: linear-gradient(145deg, #24425c, #162b3d);
    color: #dbeeff;
}

button.action-key {
    background: linear-gradient(145deg, #5c3b28, #3b2316);
    color: #ffaa77;
}